Practice Test 6 - High School Physics

20 questions. Answer them in any order, then submit to see your score and every explanation.

Two water waves approach a seawall. Wave A has amplitude $A_A = 1.5\ \text{m}$ and Wave B has amplitude $A_B = 0.50\ \text{m}$ . Assuming both are in the same conditions and $E \propto A^2$ , how do their energies compare (ratio $E_A/E_B$ )?
A 1.5 kg cart on a level track is attached to a spring ( $k = 100\,\text{N/m}$ ). The spring is stretched 0.30 m and released. At the moment the cart passes through the spring's unstretched length, its speed is 2.0 m/s. In this system, which statement correctly compares energies at that instant (ignoring friction)?
A $0.80\,\text{kg}$ ball is dropped from rest from a height of $10\,\text{m}$ (take $g=10\,\text{m/s}^2$ ). Just before hitting the ground, what is its kinetic energy?
A wave on a rope has a measured wavelength of $\lambda = 2.5\ \text{m}$ . The wave speed on the rope is $v = 5.0\ \text{m/s}$ . What is the frequency $f$ ? Use $f = v/\lambda$ .
A $2\,\text{kg}$ cart moving right at $5\,\text{m/s}$ collides inelastically with a $3\,\text{kg}$ cart at rest. After the collision, the carts move with speeds $1\,\text{m/s}$ (Cart A) and $3\,\text{m/s}$ (Cart B), both to the right. Which set of totals correctly verifies energy conservation when thermal/sound energy is included?
A 2 km campus intercom system can be built either as analog audio over copper pairs or as a digital system that samples audio and sends bits with simple error detection. The campus has moderate electromagnetic interference from motors and fluorescent lights. Which statement best compares performance as interference increases?
A single circular loop of area $A$ is in a uniform magnetic field $B$ . The loop is rotated so that the angle between the field and the loop's normal changes from $\theta=0^\circ$ to $\theta=90^\circ$ in a short time. Which statement correctly describes what causes the induced EMF?
A $15\,\text{kg}$ box is pushed across a horizontal floor by a force of $F_{\text{app}}=50\,\text{N}$ directed $37^\circ$ below the horizontal (downward and to the right). The box moves at constant velocity. Take $g=10\,\text{m/s}^2$ . What is the magnitude of the normal force $F_N$ on the box?
A chandelier hangs at rest from the ceiling by a chain. Consider the chain–chandelier interaction. Which pair of forces is an action-reaction pair?
A laser beam passes through two closely spaced slits and forms alternating bright and dark bands on a distant screen. The pattern remains even when the light intensity is reduced so much that detections occur one at a time, yet the overall distribution still builds into an interference pattern. Which model is needed to explain the alternating bright and dark bands?
A beam of light passes through two narrow slits and produces an interference pattern on a screen. However, the screen records light as individual localized dots (each detection event is a single spot), and the interference pattern appears only after many dots accumulate. What does this combination of observations most strongly suggest?
A $12\,\text{kg}$ crate is pulled across a horizontal floor at constant velocity by a rope that exerts an applied force $F_{\text{app}}=60\,\text{N}$ to the right (→). The forces on the crate are: weight $F_g$ downward (↓), normal force $F_N$ upward (↑), applied force $F_{\text{app}}$ to the right (→), and kinetic friction $F_f$ to the left (←). What is the magnitude of the friction force $F_f$ on the crate?
A student places a metal spoon (stainless steel) into a mug of hot water at 80°C in a 22°C room. After 2 minutes, the spoon handle (sticking out into the air) feels warmer even though it never touched the water. In this scenario, which thermal energy transfer mechanism is primarily responsible for warming the spoon handle along the spoon? (hot water → spoon bowl → spoon handle)
A $3.0\,\text{kg}$ box slides down a $5.0\,\text{m}$ -high ramp and reaches the bottom with speed $8.0\,\text{m/s}$ (take $g=10\,\text{m/s}^2$ ). The bottom is the $PE_g=0$ reference. Which equation correctly applies conservation of energy for this situation, including thermal energy from friction?
A $0.50\,\text{kg}$ metal block at $80^\circ\text{C}$ is placed in contact with a $0.50\,\text{kg}$ metal block at $20^\circ\text{C}$ on an insulating surface (no energy exchange with the surroundings). During this interaction, which statement best describes the energy transfer?
A proton ( $m_p=1.67\times10^{-27}\,\text{kg}$ , $q_p=+1.6\times10^{-19}\,\text{C}$ ) and an electron ( $m_e=9.11\times10^{-31}\,\text{kg}$ , $q_e=-1.6\times10^{-19}\,\text{C}$ ) are separated by some distance $r$ . Which statement is correct about the dependence of the ratio $F_{\text{elec}}/F_{\text{grav}}$ on $r$ ?
A current-carrying wire in a uniform magnetic field experiences a force $F=BIL$ (wire is perpendicular to $\vec B$ ). In an experiment, $B=0.50\ \text{T}$ , $I=2.0\ \text{A}$ , and $L=0.30\ \text{m}$ . The wire segment is free to slide and moves $d=0.40\ \text{m}$ while the current is maintained. How much energy is transferred to the wire's motion by the magnetic force?
A single circular loop is connected to a galvanometer. The loop is moved sideways through a region where the magnetic field is uniform and points straight upward. The loop's plane stays horizontal the whole time (so its area and orientation relative to $B$ do not change). Which statement best predicts what the galvanometer shows while the loop is entirely within the uniform-field region?
Two small conducting spheres can be treated as point charges. Sphere A has charge $q_1 = +2.0\,\mu\text{C}$ and sphere B has charge $q_2 = +5.0\,\mu\text{C}$ . Their centers are separated by $r = 0.30\,\text{m}$ . Using Coulomb's constant $k = 9.0 \times 10^9\,\text{N}\cdot\text{m}^2/\text{C}^2$ , what is the magnitude of the electric force between them (in N)?
A battery charger draws $P_{in}=120\ \text{W}$ from the wall outlet. It stores useful chemical energy at a rate of $P_{out}=102\ \text{W}$ in the battery; the rest becomes waste heat. What is the charger efficiency $\eta$ (as a percentage)?

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