Evidence of Energy Change - Middle School Physical Science

1. Which observation is evidence kinetic energy became thermal energy in a collision: temperature rise or color change?

   Temperature rise. Heat indicates KE was converted to thermal energy.

2. Which change is direct evidence that an object has gained kinetic energy?

   An increase in speed. Kinetic energy depends on $v^2$, so faster speed means more KE.

3. Identify the evidence of increased kinetic energy when an object is compressed and released by a spring.

   The object speeds up after release. Stored elastic PE converts to KE upon release.

4. Identify the evidence that kinetic energy was transferred to sound energy during a collision.

   Sound is produced (a loud impact or noise). Impact energy creates vibrations we hear as sound waves.

5. Identify the evidence of kinetic energy increase when an object goes from rest to moving.

   Speed changes from $0$ to $>0$. Object gains kinetic energy when it starts moving from rest.

6. Which observation is evidence that kinetic energy changed into deformation energy during an impact?

   The object dents or changes shape and slows down. Shape change while slowing shows $KE$ converted to deformation energy.

7. Which observation is evidence that kinetic energy was transferred by friction: warming surfaces or cooling surfaces?

   Warming surfaces. Friction converts kinetic energy to heat.

8. What evidence shows an object has increased kinetic energy during an interaction?

   Its speed increases after the interaction. Higher speed means more kinetic energy since $KE \propto v^2$.

9. A cart slows from $10\ \text{m/s}$ to $5\ \text{m/s}$. How does $KE$ change if mass is constant?

   It decreases to $\frac{1}{4}$ of the original. Speed halves, so $KE$ becomes $(\frac{1}{2})^2 = \frac{1}{4}$ of original.

10. What is evidence that kinetic energy was converted to light during an interaction (for example, scraping metal)?

    Light or sparks are produced. KE converts to electromagnetic energy we see as light.

11. What observation is evidence that kinetic energy became gravitational potential energy?

    The object moved to a higher height. Work against gravity converts $KE$ to gravitational $PE$.

12. A moving object comes to rest due to friction. Where did most of its kinetic energy go?

    Thermal energy in the object and surfaces. Friction converts kinetic energy into heat.

13. An object comes to rest after sliding. Which interaction force is evidence for kinetic energy loss?

    Friction with the surface. Friction converts KE to thermal energy, slowing the object.

14. Which has greater kinetic energy: mass $m$ at speed $v$ or mass $2m$ at speed $v$?

    The object with mass $2m$. Double mass doubles KE when speed is constant.

15. Which change in speed shows a decrease in kinetic energy if mass stays constant?

    Speed decreases. Lower speed means less kinetic energy when mass is constant.

16. A $1\,\text{kg}$ object slows from $10\,\text{m/s}$ to $5\,\text{m/s}$. Did $KE$ increase or decrease?

    Decreased. Speed halved, so $KE$ decreased by factor of $2^2 = 4$.

17. Which option indicates kinetic energy is being transferred by a force: no acceleration or acceleration?

    Acceleration. Force causes acceleration, which changes velocity and thus $KE$.

18. What observable evidence shows kinetic energy changed into thermal energy during braking?

    Brakes or wheels heat up while speed decreases. KE converts to heat through friction during braking.

19. Identify the evidence that kinetic energy was transferred to thermal energy during friction.

    Temperature increases (object or surroundings warm up). Friction converts motion to heat through molecular vibrations.

20. Identify the evidence that kinetic energy was transferred to sound during an interaction.

    Sound is produced (a loud impact or vibration). Kinetic energy converts to air vibrations we hear.

21. A $2\,\text{kg}$ object speeds up from $3\,\text{m/s}$ to $6\,\text{m/s}$. Did $KE$ increase or decrease?

    Increased. Speed doubled, so $KE$ increased by factor of $2^2 = 4$.

22. What happens to kinetic energy if an object's speed doubles from $v$ to $2v$ (mass constant)?

    Kinetic energy becomes $4$ times larger. Since $KE \propto v^2$, doubling speed quadruples kinetic energy.

23. Identify the evidence that kinetic energy was transferred from one object to another in a collision.

    One object slows while the other speeds up. Momentum and energy conserve; $KE$ transfers between objects.

24. Which option is evidence that kinetic energy increased when falling: speed increases or height increases?

    Speed increases. Falling objects speed up as gravitational $PE$ converts to $KE$.

25. What happens to kinetic energy if speed doubles while mass stays constant?

    It becomes $4$ times larger. Since $KE \propto v^2$, doubling $v$ quadruples KE.

26. Which change in speed $v$ is direct evidence that an object's kinetic energy changed?

    A change in speed (speeding up or slowing down). Since $KE \propto v^2$, any speed change alters kinetic energy.

27. What is kinetic energy in terms of mass and speed?

    $KE=\frac{1}{2}mv^2$. Energy of motion depends on mass and speed squared.

28. Which observation is evidence that kinetic energy changed into sound energy during an interaction?

    A sound is produced. Sound production shows kinetic energy converted to sound waves.

29. What observable evidence shows kinetic energy was transferred to thermal energy in a collision?

    Objects become warmer after the interaction. KE converts to thermal energy, raising temperature.

30. Which observation is evidence that kinetic energy increased because work was done on an object?

    A push or pull causes the object to speed up. Work done by force increases object's KE.

31. Which change in speed indicates a decrease in kinetic energy for the same object?

    Speed decreases ($v$ decreases). Lower velocity means less kinetic energy since $KE \propto v^2$.

32. What observable change is direct evidence that an object's kinetic energy increased?

    Its speed increased. Higher speed means more kinetic energy since $KE \propto v^2$.

33. Identify the evidence that kinetic energy was transferred to light energy during an interaction.

    Light is emitted (spark or glow). High-energy impacts can excite atoms to emit photons.

34. Which change in speed is direct evidence that an object's kinetic energy increased?

    Speed increased. KE increases when velocity increases since $KE \propto v^2$.

35. Which observation is evidence that kinetic energy decreased during an interaction?

    The object slows down after the interaction. Lower speed means less kinetic energy since $KE \propto v^2$.

36. Which change is direct evidence that an object's kinetic energy increased?

    Its speed increased. KE increases when velocity increases since $KE \propto v^2$.

37. Which has greater kinetic energy for the same mass: speed $3\ \text{m/s}$ or $6\ \text{m/s}$?

    $6\ \text{m/s}$. Higher speed gives more KE since $KE \propto v^2$.

38. Which observation is evidence that kinetic energy became thermal energy during an interaction?

    Temperature increase (warming). KE converts to molecular motion, raising temperature.

39. What happens to kinetic energy if speed doubles but mass stays the same?

    It becomes $4$ times larger. Since $KE \propto v^2$, doubling speed quadruples KE.

40. Which option is evidence that kinetic energy increased due to work done by a push or pull?

    The object speeds up in the direction of the force. Force does positive work, adding energy and increasing speed.

41. Identify the evidence that kinetic energy was transferred to elastic potential energy.

    An object is compressed or stretched (spring, rubber band). Motion energy stores as elastic deformation energy.

42. Identify the evidence that kinetic energy was transferred to thermal energy in a collision.

    Temperature increase of objects or surroundings. Lost kinetic energy converts to molecular motion (heat).

43. What is the best evidence that energy stayed kinetic (not mostly thermal) in a collision?

    Little heating and objects rebound with high speed. Elastic collisions conserve KE; inelastic ones convert it to heat.

44. What observation is evidence that kinetic energy was stored as elastic potential energy in a compressed spring?

    A spring compresses or stretches during the interaction. Motion energy converts to elastic potential energy in the spring.

45. What is the kinetic energy ratio if speed triples: $\frac{KE_2}{KE_1}$ when $v_2 = 3v_1$?

    $\frac{KE_2}{KE_1} = 9$. KE is proportional to $v^2$, so tripling $v$ increases KE by $3^2$.

46. What happens to kinetic energy if an object's speed is cut in half and mass stays constant?

    It becomes $\frac{1}{4}$ as large. KE varies with $v^2$, so halving speed gives $\frac{1}{4}$ KE.

47. If speed halves from $v$ to $\frac{1}{2}v$, by what factor does kinetic energy change?

    It becomes $\frac{1}{4}$ as large. Since $KE \propto v^2$, halving $v$ gives $(\frac{1}{2})^2 = \frac{1}{4}$ times $KE$.

48. Choose the correct comparison: if $v_2 = 3v_1$, what is $\frac{KE_2}{KE_1}$ for the same mass?

    $\frac{KE_2}{KE_1} = 9$. Since $KE \propto v^2$, tripling speed gives $3^2 = 9$ times KE.

49. Which has greater kinetic energy: $m=2\,\text{kg}, v=3\,\text{m/s}$ or $m=2\,\text{kg}, v=4\,\text{m/s}$?

    The object with $v=4\,\text{m/s}$. Higher speed means more KE when mass is equal.

50. Identify the evidence that an object gained kinetic energy during an interaction.

    Its speed increased after the interaction. Higher speed means higher $KE$ since $KE \propto v^2$.

51. Which interaction evidence suggests kinetic energy became thermal energy: temperature rises or temperature falls?

    Temperature rises. Friction converts kinetic energy to thermal energy.

52. An object's speed changes from $3\ \text{m/s}$ to $6\ \text{m/s}$. How does $KE$ change if mass is constant?

    It increases by a factor of $4$. Speed doubles, so $KE$ increases by $(2)^2 = 4$.

53. A $2\ \text{kg}$ cart changes speed from $3\ \text{m/s}$ to $5\ \text{m/s}$; what is $\Delta KE$?

    $16\ \text{J}$. $KE_f - KE_i = \frac{1}{2}(2)(25) - \frac{1}{2}(2)(9) = 25 - 9 = 16\ \text{J}$.

54. Identify the best evidence that total kinetic energy was not conserved in a real collision.

    Some energy changed into heat, sound, or deformation. Energy transforms to other forms in inelastic collisions.

55. Which observation is evidence that kinetic energy decreased due to friction during sliding?

    The object slows down and the surface warms. Friction converts KE to thermal energy.

56. A moving cart hits a spring and stops briefly. What is the evidence that its kinetic energy decreased?

    Its speed becomes $0\,\text{m/s}$ at maximum compression. Zero speed means zero $KE$; all energy stored in compressed spring.

57. What is evidence that kinetic energy was converted to thermal energy during an interaction?

    Temperature increases due to friction. Moving particles' KE converts to thermal motion.

58. An object's mass doubles while speed stays constant; by what factor does its kinetic energy change?

    It becomes $2\times$ larger. Since $KE \propto m$, doubling mass doubles energy.

59. Which observation is evidence that kinetic energy increased during an interaction?

    The object speeds up after the interaction. Higher speed means more kinetic energy since $KE \propto v^2$.

60. Identify the evidence of increased kinetic energy in a collision when a cart leaves faster.

    Higher speed after the interaction. Greater speed means more kinetic energy after the collision.

61. Calculate the kinetic energy change factor if speed doubles and mass stays constant.

    Kinetic energy becomes $4$ times larger. KE varies with $v^2$, so doubling $v$ quadruples KE.

62. Which observation is evidence that kinetic energy changed into thermal energy during a collision?

    Temperature increases (objects feel warmer). Heat generation shows kinetic energy converted to thermal energy.

63. Which observation is evidence that kinetic energy changed into sound during an interaction?

    A loud sound is produced during the interaction. Sound production indicates kinetic energy converted to sound energy.

64. State the formula for kinetic energy of an object with mass $m$ and speed $v$.

    $KE = \frac{1}{2}mv^2$. Formula shows KE depends on mass and square of velocity.

65. Which evidence best shows kinetic energy changed during an interaction: speed changed or direction changed at constant speed?

    Speed changed. Only speed changes affect $KE$; direction changes at constant speed don't.

66. A cart slows from $4\ \text{m/s}$ to $2\ \text{m/s}$. By what factor does its $KE$ change (mass constant)?

    It becomes $\frac{1}{4}$ of the original. Speed ratio is $\frac{2}{4} = \frac{1}{2}$, so $KE$ ratio is $(\frac{1}{2})^2 = \frac{1}{4}$.

67. What observation is evidence that kinetic energy became elastic potential energy in a collision?

    A spring or object compressed or stretched. Deformation stores kinetic energy as elastic potential energy.

68. What is the kinetic energy change sign if an object slows down from $6\,\text{m/s}$ to $2\,\text{m/s}$?

    Negative; kinetic energy decreases. Speed decreased, so $KE_{final} < KE_{initial}$.

69. What is the kinetic energy ratio if speed is cut in half: $\frac{KE_2}{KE_1}$ when $v_2 = \frac{1}{2}v_1$?

    $\frac{KE_2}{KE_1} = \frac{1}{4}$. KE is proportional to $v^2$, so halving $v$ reduces KE to $(\frac{1}{2})^2$.

70. Which change provides direct evidence that an object's kinetic energy decreased during an interaction?

    Its speed decreased. Lower speed means less kinetic energy since $KE \propto v^2$.

71. Which change in speed indicates an increase in kinetic energy for the same object?

    An increase in speed $v$. Since $KE \propto v^2$, higher speed means more kinetic energy.

72. A speed–time graph shows speed dropping from $8$ to $0\ \text{m/s}$. What happened to kinetic energy?

    Kinetic energy decreased to $0$. Speed went to zero, so all KE was lost.

73. What happens to kinetic energy when mass doubles and speed stays the same?

    It doubles. KE is directly proportional to mass when speed is constant.

74. What is kinetic energy in terms of an object's mass and speed?

    $KE=\frac{1}{2}mv^2$. KE depends on mass and the square of velocity.

75. If mass doubles and speed stays the same, by what factor does kinetic energy change?

    It becomes $2$ times larger. $KE \propto m$, so doubling mass doubles $KE$.

76. Which option is evidence that kinetic energy changed during a collision: mass change or speed change?

    Speed change. Only velocity affects KE during collisions; mass is conserved.

77. What observable change is direct evidence that an object's kinetic energy decreased?

    Its speed decreased. Lower speed means less kinetic energy since $KE \propto v^2$.

78. What is the kinetic energy of a $2\ \text{kg}$ object moving at $3\ \text{m/s}$?

    $9\ \text{J}$. Using $KE=\frac{1}{2}(2)(3^2)=\frac{1}{2}(2)(9)=9\ \text{J}$.

79. Which change in speed is direct evidence that an object's kinetic energy decreased?

    Speed decreased. KE decreases when velocity decreases since $KE \propto v^2$.

80. Object A has speed $2v$ and object B has speed $v$ (same mass). Which has greater kinetic energy?

    Object A. Object A has 4 times more KE since its speed is doubled.

81. Identify the best evidence of an elastic collision between two carts.

    They bounce apart with little warming or deformation. Elastic collisions conserve KE with minimal energy loss.

82. Identify the evidence of decreased kinetic energy when two objects stick together after colliding.

    Lower speed of the combined object. Combined objects move slower, showing kinetic energy was lost.

83. Which graph feature is evidence that kinetic energy increased over time, assuming mass is constant?

    A speed-versus-time graph that trends upward. Rising speed means increasing $KE$ since $KE \propto v^2$.

84. A $1\ \text{kg}$ ball has $KE=18\ \text{J}$; what is its speed using $KE=\frac{1}{2}mv^2$?

    $6\ \text{m/s}$. Solve $18 = \frac{1}{2}(1)v^2$ gives $v^2 = 36$, so $v = 6\ \text{m/s}$.

85. What observation shows kinetic energy was transferred to thermal energy during an interaction?

    Temperature increased (objects warmed up). Friction converts kinetic energy to thermal energy.

86. What is kinetic energy, expressed as a formula using mass $m$ and speed $v$?

    $KE=\frac{1}{2}mv^2$. Energy of motion depends on mass and speed squared.

87. Which observation best indicates kinetic energy changed into deformation (internal) energy?

    Objects bend, dent, or permanently change shape. KE converts to work done in deforming materials.

88. An object doubles its speed from $v$ to $2v$. By what factor does $KE$ change?

    It becomes $4$ times larger. KE proportional to $v^2$: $(2v)^2 = 4v^2$

89. Identify the sign of work when kinetic energy decreases: positive work or negative work?

    Negative work. Work removes energy from the system, decreasing KE.

90. Calculate the kinetic energy change factor if speed is cut in half and mass stays constant.

    Kinetic energy becomes $\frac{1}{4}$ as large. Halving speed reduces KE by factor of $2^2 = 4$.

91. Which option is evidence that kinetic energy changed into thermal energy during friction?

    The surfaces become warmer while the object slows. Heat generation while slowing shows $KE$ converted to thermal energy.

92. Which type of collision typically shows the most kinetic energy converted to other forms: elastic or inelastic?

    Inelastic. Objects stick together, converting more KE to other forms.

93. Which option is evidence that kinetic energy decreased as gravitational potential energy increased: rising, falling, or level?

    Rising (speed decreases). Rising objects slow as KE converts to gravitational PE.

94. Identify the evidence that kinetic energy was transferred to light during an interaction.

    Light is produced (sparks or glow). Kinetic energy converts to electromagnetic radiation.

95. What observation shows kinetic energy was transferred to sound during an interaction?

    Sound was produced (a noticeable noise). Impact vibrations convert kinetic energy to sound waves.

96. Which observation best indicates kinetic energy changed into sound energy in an interaction?

    A sound is produced during the interaction. KE converts to sound waves during the interaction.

97. Two identical masses collide and both move slower afterward. What is the kinetic energy change for the system?

    Total kinetic energy decreased. Lower speeds mean less total KE in the system.

98. A cart slows from $6\,\text{m/s}$ to $2\,\text{m/s}$. Did its kinetic energy increase or decrease?

    Decrease. Slower speed means lower kinetic energy.

99. A cart is pushed and speeds up from $2\,m/s$ to $4\,m/s$. Did its kinetic energy increase or decrease?

    Increased. Speed doubled, so KE quadrupled (from $4$ to $16$ units).

100. Choose the correct comparison: at the same speed, which has greater kinetic energy, mass $m$ or $2m$?

     Mass $2m$ has twice the kinetic energy. KE is proportional to mass when speed is constant.

101. Identify the evidence that kinetic energy was transferred during a collision.

     One object slows while the other speeds up. KE transfers from the slowing object to the speeding one.

102. Identify the evidence that kinetic energy decreased because it converted to gravitational potential energy.

     An object slows down while moving upward. Motion energy converts to gravitational potential as height increases.

103. A ball's speed changes from $10\,\text{m/s}$ to $5\,\text{m/s}$. What happens to its kinetic energy?

     It decreases to $\frac{1}{4}$ of the original. Speed halved ($\frac{5}{10} = \frac{1}{2}$), so KE becomes $(\frac{1}{2})^2 = \frac{1}{4}$.

104. Which observation is evidence that kinetic energy changed into thermal energy during an interaction?

     Temperature increases. Heat generation shows kinetic energy converted to thermal energy.

105. Which observation is evidence that kinetic energy changed into sound energy in a collision?

     A sound is produced while the objects lose speed. Sound production while slowing shows $KE$ converted to sound energy.

106. Which change is direct evidence that an object has lost kinetic energy?

     A decrease in speed. Lower speed means less $v^2$ in the KE formula.

107. What is evidence that kinetic energy was converted to sound energy during an interaction?

     A noticeable sound is produced. KE converts to air vibrations we hear as sound.

108. Identify the evidence that kinetic energy was converted to gravitational potential energy while moving upward.

     Speed decreases as height increases. Slowing while rising shows $KE$ converting to gravitational $PE$.

109. What is the unit of kinetic energy in the SI system?

     Joule (J). The SI unit for all forms of energy.

110. Which observation is evidence that kinetic energy increased due to a push or pull doing work?

     The object speeds up while force acts. Acceleration shows work done by force increases kinetic energy.

111. Identify the evidence that gravitational potential energy changed into kinetic energy as an object falls.

     The object speeds up as it moves downward. Falling objects gain speed as gravitational PE converts to $KE$.

112. Which observation best indicates kinetic energy changed into thermal energy in an interaction?

     The objects or surfaces become warmer. KE converts to thermal energy, increasing temperature.

113. Which variable change is direct evidence that an object's kinetic energy changed?

     A change in speed, $v$. KE depends on $v^2$, so speed changes directly indicate KE changes.

114. What is one clear sign that kinetic energy was transferred to another object in a collision?

     The second object starts moving or speeds up. KE transfers when one object sets another in motion.

115. Which observation is evidence that kinetic energy became deformation energy during an interaction?

     Object bends, dents, or compresses. KE converts to potential energy stored in deformed material.

116. Which measurement is direct evidence of a change in kinetic energy: mass change or speed change?

     Speed change. Only speed affects KE when mass is constant ($KE \propto v^2$).

117. Which observation is evidence kinetic energy was transferred to deformation: object dents or object glows?

     Object dents (deforms). Lost KE does work to permanently deform the material.

118. Which graph feature is evidence that kinetic energy is increasing over time?

     Speed $v$ increases with time. Rising speed means KE is increasing.

119. Which evidence shows kinetic energy decreased during an interaction: speed increased or speed decreased?

     Speed decreased. Lower speed means less kinetic energy since $KE \propto v^2$.

120. What is kinetic energy in terms of mass $m$ and speed $v$?

     $KE = \frac{1}{2}mv^2$. Energy of motion depends on mass and speed squared.

121. Which observation is evidence kinetic energy was transferred to thermal energy: temperature rises or color changes?

     Temperature rises. Lost KE converts to thermal energy, raising temperature.

122. Which measurement best indicates a change in kinetic energy: mass, temperature, or speed?

     Speed. Only speed directly appears in the kinetic energy formula.

123. Which observation is direct evidence kinetic energy changed during an interaction: speed change or mass change?

     Speed change. Speed directly determines KE; mass typically stays constant.

124. A moving cart hits a bumper and stops. Identify the kinetic energy of the cart after the collision.

     $0\ \text{J}$. No motion means no KE ($v = 0$).

125. If an object's speed stays constant, which variable must change for kinetic energy to change?

     Mass $m$. From $KE = \frac{1}{2}mv^2$, only $m$ can vary when $v$ is fixed.

126. What is kinetic energy, in words, for a moving object?

     Energy of motion. Kinetic energy is the energy an object has due to its motion.

127. Which interaction is evidence that kinetic energy changed: a collision that changes speed or motion at constant speed?

     A collision that changes speed. Speed changes indicate $v$ changed, thus KE changed.

128. Two equal-mass carts collide and bounce apart faster than before; what happened to total kinetic energy?

     It increased. Extra energy came from stored potential (springs, explosives, etc.).

129. Which statement best describes kinetic energy during braking with friction?

     Kinetic energy decreases; thermal energy increases. Friction converts motion energy to heat during braking.

130. What happens to kinetic energy if an object's speed doubles and mass stays constant?

     It becomes $4$ times larger. KE varies with $v^2$, so doubling speed quadruples KE.

131. Which observation is evidence kinetic energy was transferred to light in an interaction: spark/flash or silence?

     Spark or flash of light. High-energy impacts can produce light.

132. What happens to kinetic energy if mass doubles and speed stays constant?

     It becomes $2$ times larger. KE is directly proportional to mass when speed is constant.

133. Identify the evidence that kinetic energy changed: constant speed or changing speed during interaction?

     Changing speed during interaction. Velocity changes indicate KE changes; constant speed means constant KE.

134. Which change provides direct evidence that an object's kinetic energy increased during an interaction?

     Its speed increased. Higher speed means more kinetic energy since $KE \propto v^2$.

135. Which observation is evidence that kinetic energy changed into deformation energy during an interaction?

     An object bends, dents, or stretches. Shape changes show kinetic energy went into deforming the material.

136. Which option is evidence that kinetic energy decreased due to friction: object warms up or object cools down?

     Object warms up. Friction converts kinetic energy to thermal energy, warming objects.

137. Which object has greater kinetic energy: $m=1\ \text{kg}, v=6\ \text{m/s}$ or $m=2\ \text{kg}, v=4\ \text{m/s}$?

     $m=1\ \text{kg}, v=6\ \text{m/s}$. First has $KE=18\ \text{J}$, second has $KE=16\ \text{J}$.

138. What is kinetic energy ($KE$) in terms of mass $m$ and speed $v$?

     $KE = \frac{1}{2}mv^2$. Kinetic energy depends on mass and the square of velocity.

139. Identify the kinetic energy change sign if an object speeds up from $2\,\text{m/s}$ to $6\,\text{m/s}$.

     Positive; kinetic energy increases. Speed increased, so $KE_{final} > KE_{initial}$.

140. Which collision best indicates kinetic energy stayed mostly kinetic: objects bounce apart or stick together?

     Objects bounce apart. Elastic collisions conserve most kinetic energy.

141. An object's speed is cut in half from $v$ to $\frac{v}{2}$. By what factor does $KE$ change?

     It becomes $\frac{1}{4}$ as large. KE proportional to $v^2$: $(\frac{v}{2})^2 = \frac{v^2}{4}$

142. A moving ball hits a wall and rebounds slower. What happened to the ball's kinetic energy?

     It decreased. Rebounding slower means less speed, thus less KE.

143. If speed doubles and mass stays the same, by what factor does kinetic energy change?

     It becomes $4$ times larger. $KE \propto v^2$, so doubling $v$ quadruples $KE$.

144. What happens to kinetic energy if mass doubles but speed stays the same?

     It doubles. KE is directly proportional to mass when speed is constant.

145. Which graph feature is evidence kinetic energy is increasing: speed-time line slopes up or slopes down?

     Speed-time line slopes up. Upward slope shows speed increasing, thus KE increasing.

146. A cart slows from $6\,\text{m/s}$ to $2\,\text{m/s}$ with the same mass. Did kinetic energy increase or decrease?

     Decrease. Speed dropped from $6$ to $2$ m/s, so kinetic energy decreased.

147. Identify the evidence that kinetic energy increased due to gravitational potential energy converting to kinetic energy.

     An object speeds up while moving downward. Gravity converts potential energy to kinetic as height decreases.

148. A moving object comes to rest. What is the kinetic energy after it stops, in terms of $v$?

     $KE = 0$ when $v = 0$. No motion means no kinetic energy by definition.

149. What happens to kinetic energy when speed is cut in half and mass stays the same?

     It becomes $\frac{1}{4}$ as large. KE depends on speed squared, so halving speed gives one-fourth energy.

150. Which option is evidence that kinetic energy increased due to gravity: rising, falling, or staying level?

     Falling (speed increases). Gravity accelerates falling objects, increasing their KE.

151. Which graph feature is evidence that kinetic energy is increasing over time for constant mass?

     A speed-vs-time graph with a positive slope. Positive slope means speed increasing, so $KE$ rises.

152. What is kinetic energy, in terms of an object's mass and speed?

     $KE=\frac{1}{2}mv^2$. Energy of motion depends on mass and velocity squared.

153. A $3\ \text{kg}$ cart slows from $6\ \text{m/s}$ to $3\ \text{m/s}$. By what factor does $KE$ change?

     It decreases by a factor of $4$. Initial $KE=54\ \text{J}$, final $KE=13.5\ \text{J}$, so factor is $4$.

154. Which observation is evidence that kinetic energy was stored as elastic potential energy?

     A spring or rubber band is compressed or stretched. KE converts to elastic PE in deformed materials.

155. A cart's speed changes from $2\,\text{m/s}$ to $6\,\text{m/s}$. What happens to its kinetic energy?

     It increases by a factor of $9$. Speed tripled ($\frac{6}{2} = 3$), so KE increases by $3^2 = 9$.

156. Identify the sign of kinetic energy change if an object goes from rest to $4\ \text{m/s}$.

     Kinetic energy increased. Speed rose from 0 to 4 m/s, so KE increased.

157. Identify the sign of kinetic energy change if an object's speed decreases during an interaction.

     $\Delta KE<0$. Lower speed means lower KE, so change is negative.

158. What visible change is evidence that kinetic energy caused deformation in a collision?

     A dent, bend, or permanent shape change. Kinetic energy does work to permanently reshape material.

159. What is kinetic energy, expressed as a formula in terms of mass $m$ and speed $v$?

     $KE = \frac{1}{2}mv^2$. Kinetic energy depends on mass and the square of velocity.

160. Which observation is evidence that kinetic energy increased because work was done on an object?

     A push or pull causes speed to increase. Forces doing work add energy, increasing object's kinetic energy.

161. Choose the correct comparison: if speed triples, kinetic energy changes by a factor of $3$ or $9$?

     $9$. KE varies with $v^2$, so tripling speed gives $3^2 = 9$ times KE.

162. Identify the evidence that kinetic energy decreased when a force acts opposite the direction of motion.

     Speed decreases after the force acts. Opposing force does negative work, decreasing KE.

163. Which has greater kinetic energy: same mass at speed $v$ or at speed $2v$?

     The object at speed $2v$. Higher speed means more KE since $KE \propto v^2$.

164. Which observation is evidence that kinetic energy was conserved in an interaction with negligible friction?

     Total $KE$ before is approximately equal to total $KE$ after. No energy lost means elastic collision with energy conservation.

165. A $3\ \text{kg}$ cart slows from $4\ \text{m/s}$ to $2\ \text{m/s}$. Identify whether $KE$ changed by more or less than half.

     More than half (it becomes $\frac{1}{4}$ as large). KE ratio: $\frac{(2)^2}{(4)^2} = \frac{4}{16} = \frac{1}{4}$

166. What is kinetic energy, expressed as a formula using mass and speed?

     $KE=\frac{1}{2}mv^2$. Kinetic energy equals half the mass times velocity squared.

167. Identify the sign of work on an object when its kinetic energy increases: positive or negative work?

     Positive work. Work-energy theorem: positive work increases KE.

168. Choose the best evidence that kinetic energy increased due to a motor: constant speed or increasing speed?

     Increasing speed. Acceleration shows net force is adding energy to the system.

169. Which observation is evidence that kinetic energy became sound energy during an interaction?

     Sound is produced. KE converts to air vibrations we hear as sound.

170. What happens to kinetic energy if an object's mass doubles and speed stays constant?

     It doubles. KE is directly proportional to mass when speed is constant.

171. Which change is direct evidence that an object's kinetic energy decreased?

     Its speed decreased. KE decreases when velocity decreases since $KE \propto v^2$.

172. Identify the evidence for decreased kinetic energy when friction acts on a moving object.

     Object slows down (speed decreases). Friction converts KE to thermal energy, reducing speed.

173. Identify the evidence of kinetic energy decreasing in a collision: rebound faster or move slower afterward?

     Move slower afterward. Slower speed means lower $v$, thus lower KE.

174. What observable evidence shows kinetic energy was transferred to light energy during an interaction?

     Light is emitted (spark, glow, or flash). KE converts to electromagnetic radiation.

175. What happens to kinetic energy if mass doubles from $m$ to $2m$ at the same speed $v$?

     Kinetic energy doubles. Since $KE \propto m$, doubling mass doubles kinetic energy at same speed.

176. What is the evidence that kinetic energy remained the same during an interaction?

     Speed stays constant (no change in $v$). No speed change means no kinetic energy change.

177. In an elastic collision, what evidence suggests total kinetic energy stayed about the same?

     Total speed pattern before and after is similar. Elastic collisions conserve total kinetic energy of the system.

178. What observable evidence shows kinetic energy was transferred to sound energy during an interaction?

     A sound is produced (a bang, thud, or crash). KE converts to sound waves during impact.

179. Which change increases kinetic energy: doubling speed $v$ or doubling mass $m$ (with the other constant)?

     Doubling $v$ increases $KE$ more (by a factor of $4$). Since $KE \propto v^2$, doubling $v$ quadruples $KE$; doubling $m$ only doubles it.

180. What is the evidence that kinetic energy changed into deformation energy during an impact?

     Objects dent, crumple, or change shape. Shape changes absorb KE during plastic deformation.

181. Which interaction typically shows kinetic energy decreasing due to friction with a surface?

     A sliding object slows down and the surface warms. Friction converts kinetic energy to thermal energy.

182. If speed triples and mass stays the same, by what factor does kinetic energy change?

     It becomes $9$ times larger. $KE \propto v^2$, so tripling $v$ increases $KE$ by $3^2$.

183. Identify the evidence of kinetic energy increasing during an interaction: an object speeds up or slows down?

     Speeds up. Increasing speed increases $v^2$ in the kinetic energy formula.

184. What is the formula for kinetic energy of an object with mass $m$ and speed $v$?

     $KE=\frac{1}{2}mv^2$. Shows kinetic energy depends on mass and velocity squared.

185. Identify the evidence that kinetic energy increased when a force acts in the direction of motion.

     Speed increases after the force acts. Force along motion does positive work, increasing KE.

186. A cart goes from $6\ \text{m/s}$ to $2\ \text{m/s}$. Identify whether $KE$ increased or decreased.

     Decreased. Speed went down, so KE decreased.

187. Which option best indicates kinetic energy changed: change in direction only or change in speed?

     Change in speed. KE depends on speed magnitude, not direction.

188. Which quantity must change for kinetic energy to change if mass stays constant?

     Speed $v$. From $KE=\frac{1}{2}mv^2$, only $v$ affects $KE$ when $m$ is fixed.

189. In a perfectly elastic collision, what happens to the total kinetic energy of the colliding objects?

     It stays the same. Elastic collisions conserve total kinetic energy.

190. Which observation is evidence that kinetic energy changed into light energy during an interaction?

     Light is produced (spark or glow). Light emission shows kinetic energy converted to electromagnetic energy.

191. Which observation is evidence kinetic energy was transferred to sound in an interaction: loud noise or dim light?

     Loud noise. Lost KE converts to sound waves during impact.

192. What is kinetic energy, in words, for a moving object?

     Energy of motion. Kinetic energy is the energy an object has due to its motion.

193. A cart goes from $2\ \text{m/s}$ to $5\ \text{m/s}$. Identify whether $KE$ increased or decreased.

     Increased. Speed went up, so KE increased.

194. Identify the evidence of kinetic energy decreasing during an interaction: an object stops or starts moving?

     Stops moving. Zero velocity means zero kinetic energy.

195. What happens to kinetic energy if an object's speed is cut in half from $v$ to $\frac{v}{2}$ (mass constant)?

     Kinetic energy becomes $\frac{1}{4}$ as large. Since $KE \propto v^2$, halving speed reduces kinetic energy to one-fourth.

196. Identify the evidence of increased kinetic energy when mass stays constant: momentum increases or speed increases?

     Speed increases. KE depends on speed squared, not just momentum.

197. Calculate $KE$ for $m = 2\ \text{kg}$ and $v = 3\ \text{m/s}$ using $KE = \frac{1}{2}mv^2$.

     $9\ \text{J}$. $KE = \frac{1}{2}(2)(3)^2 = \frac{1}{2}(2)(9) = 9\ \text{J}$

198. Which measurement is most directly used to compare kinetic energy before and after an interaction?

     Speed (and mass if it changes). KE formula uses speed and mass as its variables.

199. Which observation best indicates kinetic energy decreased in a crash: more bounce-back or more crumpling?

     More crumpling. Crumpling absorbs KE; bouncing preserves it.

200. Identify the evidence in a crash that kinetic energy was dissipated (not kept as motion).

     Deformation, heat, and sound are produced. These forms show $KE$ transformed to other energy types.

201. What is the kinetic energy of a $1\ \text{kg}$ ball moving at $4\ \text{m/s}$?

     $8\ \text{J}$. $KE = \frac{1}{2}(1)(4)^2 = \frac{1}{2}(1)(16) = 8\ \text{J}$

202. A ball hits a wall and rebounds with smaller speed. Did its kinetic energy increase or decrease?

     Decreased. Lower rebound speed means less KE after collision.

203. If an object's mass stays constant, which variable must change for kinetic energy to change?

     Speed $v$. From $KE = \frac{1}{2}mv^2$, only $v$ can vary when $m$ is fixed.

204. Two identical carts collide and stick together. Which is evidence kinetic energy decreased: they stick or they bounce apart?

     They stick together. Sticking together indicates inelastic collision with energy loss.

205. What evidence from motion shows kinetic energy increased during an interaction?

     The object's speed increased. Higher speed means more kinetic energy since $KE \propto v^2$.

206. Which option is the best evidence of kinetic energy transferred by contact: push, pull, or heat?

     Push or pull (a force doing work). Forces transfer energy through work done on objects.

207. A ball speeds up from $3\,\text{m/s}$ to $5\,\text{m/s}$ with the same mass. Did kinetic energy increase or decrease?

     Increase. Speed rose from $3$ to $5$ m/s, so kinetic energy increased.

208. What evidence from motion shows kinetic energy decreased during an interaction?

     The object's speed decreased. Lower speed means less kinetic energy since $KE \propto v^2$.

209. Identify the sign of work when kinetic energy increases: positive work or negative work?

     Positive work. Work adds energy to the system, increasing KE.

210. A compressed spring launches a cart from rest. What happened to the cart's kinetic energy during launch?

     It increased. Spring's potential energy converted to cart's kinetic energy.

211. Two identical carts stick together after collision and move slower. What happens to total kinetic energy?

     Total kinetic energy decreases. Lower final speed means less total KE after collision.

212. What relationship links work and kinetic energy change for an object?

     $W_{\text{net}} = \Delta KE$. The work-energy theorem relates net work to KE change.

213. Which interaction is most likely to increase an object's kinetic energy: push forward or friction opposite motion?

     A push forward. Force in motion direction increases speed and KE.

214. Which quantity must be compared to identify a change in kinetic energy during an interaction?

     Speed before versus speed after the interaction. Kinetic energy depends on speed, so speed changes reveal $KE$ changes.

215. What is the kinetic energy of a $4\ \text{kg}$ object moving at $2\ \text{m/s}$?

     $8\ \text{J}$. Using $KE=\frac{1}{2}(4)(2^2)=\frac{1}{2}(4)(4)=8\ \text{J}$.

216. What observation is evidence that kinetic energy was transferred to deformation during a collision?

     Objects dent, bend, or permanently change shape. Energy goes into breaking molecular bonds and reshaping material.

217. A $1\ \text{kg}$ cart speeds up from $2\ \text{m/s}$ to $4\ \text{m/s}$. By what factor does $KE$ change?

     It increases by a factor of $4$. Initial $KE=2\ \text{J}$, final $KE=8\ \text{J}$, so factor is $4$.

218. Which change in speed indicates a decrease in kinetic energy for the same object?

     A decrease in speed $v$. Since $KE \propto v^2$, lower speed means less kinetic energy.

219. In an inelastic collision (objects deform or stick), what typically happens to total kinetic energy?

     It decreases. Some KE converts to heat, sound, or deformation.

220. For the same speed, how does kinetic energy change when mass doubles from $m$ to $2m$?

     It becomes $2$ times larger. Since $KE \propto m$, doubling mass doubles KE.

221. Which quantity is the most direct evidence of a change in kinetic energy: mass or speed?

     Speed. KE depends on $v^2$, so speed changes directly affect KE.

222. What evidence shows an object has decreased kinetic energy during an interaction?

     Its speed decreases after the interaction. Lower speed means less kinetic energy since $KE \propto v^2$.

223. Which evidence best indicates kinetic energy transferred from one object to another during a collision?

     One slows while the other speeds up. Energy transfers when one object loses speed while another gains it.

224. An object's speed doubles while mass stays constant; by what factor does its kinetic energy change?

     It becomes $4\times$ larger. Since $KE \propto v^2$, doubling $v$ quadruples energy.

225. What is kinetic energy in terms of mass $m$ and speed $v$?

     $KE = \frac{1}{2}mv^2$. Kinetic energy depends on mass and the square of velocity.

226. An object slows from $6\ \text{m/s}$ to $3\ \text{m/s}$ with the same mass; how does $KE$ change?

     It becomes $\frac{1}{4}$ of the original. Halving speed reduces $KE$ by factor of $2^2 = 4$.

227. Which interaction is most likely to decrease an object's kinetic energy: push forward or friction opposite motion?

     Friction opposite the motion. Friction opposes motion, reducing speed and KE.

228. Two equal-mass carts collide and stick; their combined speed is smaller than before. What happened to total kinetic energy?

     It decreased. Inelastic collisions lose energy to heat, sound, and deformation.

229. Identify the evidence that an object lost kinetic energy during an interaction.

     Its speed decreased after the interaction. Lower speed means lower $KE$ since $KE \propto v^2$.

230. Which type of collision typically shows more kinetic energy transformed to other forms: elastic or inelastic?

     Inelastic collision. Inelastic collisions lose more KE to heat and deformation.

231. Identify the evidence of kinetic energy transfer when one cart slows and the other speeds up after contact.

     Kinetic energy was transferred from the slowing cart to the speeding cart. Speed changes show $KE$ moved between objects during collision.

232. Which factor affects kinetic energy more strongly: doubling speed or doubling mass (use $KE=\frac{1}{2}mv^2$)?

     Doubling speed (it makes $KE$ $4\times$ larger). Speed is squared in the formula, mass is not.

233. What is the kinetic energy of a $2\ \text{kg}$ cart moving at $3\ \text{m/s}$?

     $9\ \text{J}$. $KE = \frac{1}{2}(2)(3)^2 = \frac{1}{2}(2)(9) = 9\ \text{J}$

234. Which change in speed shows an increase in kinetic energy if mass stays constant?

     Speed increases. Higher speed means more kinetic energy when mass is constant.

235. A ball hits the floor and rebounds to a lower height. What evidence shows kinetic energy decreased in the interaction?

     Rebound height is lower, indicating less speed after impact. Lower height means lower speed, thus less $KE$ after bounce.

236. Two carts stick together after collision. If their final speed is smaller, what happened to total kinetic energy?

     It decreased. Lower final speed means less total kinetic energy.

237. Two identical carts collide and stick together (perfectly inelastic). What is the clearest evidence that total kinetic energy decreased?

     Some energy became heat/sound/deformation; speed after is lower. Inelastic collisions always lose $KE$ to other forms.

238. Two objects have the same speed. Which has greater kinetic energy: mass $m$ or mass $2m$?

     The object with mass $2m$. At same speed, double mass means double $KE$.

239. Identify the sign of kinetic energy change if an object goes from $6\ \text{m/s}$ to $2\ \text{m/s}$.

     Kinetic energy decreased. Speed dropped from 6 to 2 m/s, so KE decreased.

240. What equation links net work and the change in kinetic energy?

     $W_{net}=\Delta KE$. Work-energy theorem: net work equals change in kinetic energy.

241. Which interaction is evidence that kinetic energy was transferred by a push: object speeds up after contact or stays still?

     Object speeds up after contact. Increased speed shows energy was added to the object.

242. If speed doubles from $v$ to $2v$, by what factor does kinetic energy change?

     It becomes $4$ times as large. Since $KE \propto v^2$, doubling $v$ gives $(2)^2 = 4$ times $KE$.

243. Identify the sign of kinetic energy change if an object's speed increases during an interaction.

     $\Delta KE>0$. Higher speed means higher KE, so change is positive.

244. What is evidence that kinetic energy was converted to deformation energy in a collision?

     Objects bend, dent, or compress. KE converts to potential energy stored in deformed materials.

245. Which observation is evidence kinetic energy was transferred to sound: louder sound or dimmer light?

     Louder sound. Impact converts kinetic energy to sound waves.

246. Which observation best indicates kinetic energy changed into light energy in an interaction?

     Light is emitted (for example, a spark). KE converts to electromagnetic radiation as light.

247. What is evidence that friction reduced an object's kinetic energy?

     The object slows down and the surface warms. Friction converts KE to thermal energy, reducing speed.

248. Identify the evidence of kinetic energy transfer when a moving cart slows and the brake pad gets hot.

     Speed decreases and temperature increases. KE converts to thermal energy via friction.

249. What happens to kinetic energy if speed doubles and mass stays constant?

     It becomes $4$ times larger. KE is proportional to $v^2$, so $(2v)^2 = 4v^2$.

250. Identify the evidence that kinetic energy changed into gravitational potential energy as an object rises.

     The object slows down as it moves upward. Rising objects lose speed as $KE$ converts to gravitational PE.

251. Which option is evidence that kinetic energy decreased even if speed is unchanged: heating, silence, or no change?

     No decrease; unchanged speed means unchanged kinetic energy. Constant speed means constant KE regardless of other factors.

252. Which option is evidence that kinetic energy increased because work was done on an object?

     A push or pull makes the object speed up. Force does positive work, increasing the object's $KE$.

253. Which observation is evidence that some kinetic energy was transformed (not conserved) in a collision?

     Total $KE$ after is less than total $KE$ before. Energy loss indicates conversion to heat, sound, or deformation.

254. An object's speed changes from $2\ \text{m/s}$ to $6\ \text{m/s}$. By what factor does $KE$ change (mass constant)?

     It increases by a factor of $9$. Speed ratio is $\frac{6}{2} = 3$, so $KE$ ratio is $3^2 = 9$.

255. For the same mass, how does kinetic energy change when speed doubles from $v$ to $2v$?

     It becomes $4$ times larger. Since $KE \propto v^2$, doubling $v$ gives $(2v)^2 = 4v^2$.

256. What happens to kinetic energy if mass doubles while speed stays constant?

     It doubles. KE is directly proportional to mass when speed is constant.

257. What happens to kinetic energy when speed doubles and mass stays the same?

     It becomes $4$ times larger. KE depends on speed squared, so doubling speed quadruples energy.

258. Which change in speed guarantees that kinetic energy increases for the same object?

     Speed increases. Since $KE \propto v^2$, any increase in speed raises KE.

259. Identify the evidence of kinetic energy decrease when a ball hits clay and does not bounce.

     It stops and does not rebound. No rebound means KE was absorbed by deformation.

260. Which option is direct evidence of decreased kinetic energy: higher speed, lower speed, or higher mass?

     Lower speed. Only speed directly affects $KE$; mass is a property, not evidence.

261. A moving ball hits a wall and stops. Identify the best evidence that its kinetic energy decreased.

     Its speed becomes $0\ \text{m/s}$. Zero speed means all kinetic energy was lost in the collision.

262. Which change in speed indicates an increase in kinetic energy for the same object?

     Speed increases ($v$ increases). Higher velocity means more kinetic energy since $KE \propto v^2$.

263. What is the kinetic energy ratio if speed doubles: $\frac{KE_2}{KE_1}$ when $v_2 = 2v_1$?

     $\frac{KE_2}{KE_1} = 4$. KE is proportional to $v^2$, so doubling $v$ quadruples KE.

264. Which observation is evidence that kinetic energy changed into deformation energy in a crash?

     Objects bend, dent, or compress. Deformation shows kinetic energy converted to changing object shape.

265. What is the unit of kinetic energy in the SI system?

     Joule (J). Named after James Joule; same unit as work and energy.

266. Two equal-mass objects interact; one speeds up while the other slows down. What is the evidence of KE transfer?

     Opposite speed changes show energy transfer. One object gains the KE that the other loses.

267. What observable evidence shows kinetic energy changed into sound during a collision?

     A sound is produced and objects slow down. KE transforms to sound waves, reducing object speeds.

268. What happens to kinetic energy if speed is cut in half but mass stays the same?

     It becomes $\frac{1}{4}$ as large. Halving speed divides KE by 4 since $KE \propto v^2$.

269. What is the evidence that friction decreased kinetic energy during motion?

     Object slows down and surfaces warm up. Friction converts KE to thermal energy, slowing objects.

Study these flashcards