Forces and Free-Body Diagrams - AP Physics C Mechanics

1. What is meant by a net external force?

   The vector sum of all external forces acting on a system. Total force from all sources outside the system boundaries.

2. What is the role of tension in a pulley system?

   Transmits force between masses. Tension provides connection force between separated objects.

3. Define tension in the context of forces.

   The pulling force transmitted along a flexible medium such as a rope. Internal force within strings, cables, or ropes under stress.

4. Which force keeps an object moving in a circular path?

   Centripetal force. Always directed toward the center of circular path.

5. What is the relationship between force and acceleration?

   Directly proportional; $F = ma$. Force and acceleration have the same direction relationship.

6. Identify the components of a force vector in two dimensions.

   Horizontal ($F_x$) and vertical ($F_y$) components. Breaking forces into perpendicular components simplifies analysis.

7. What is the effect of mass on gravitational force?

   Gravitational force increases with mass. More massive objects experience proportionally stronger gravitational attraction.

8. What is the value of the gravitational constant $G$?

   $6.674 \times 10^{-11} \text{Nm}^2/\text{kg}^2$. Universal constant determining gravitational force strength.

9. Identify the formula for net force when multiple forces act on an object.

   $F_{\text{net}} = \text{sum of all forces}$. Vector addition of all individual forces acting on object.

10. Identify the acceleration due to gravity on Earth's surface.

    $9.8 \text{m/s}^2$. Standard gravitational acceleration at Earth's surface.

11. Identify the units of force in the International System of Units.

    Newton (N). Standard SI unit equivalent to $\text{kg}\cdot\text{m/s}^2$.

12. What does the term 'frictionless surface' imply?

    No frictional force acts on the moving objects. Idealized condition where friction coefficient equals zero.

13. Identify the effect of balanced forces on an object.

    No change in motion; object remains at rest or moves uniformly. Equal opposing forces result in zero net force.

14. What is the purpose of a free-body diagram?

    To analyze the forces acting on an object. Essential tool for applying Newton's laws systematically.

15. What does a free-body diagram represent?

    All forces acting on a single object. Shows all external forces without showing the object's surroundings.

16. What is the formula for Newton's second law of motion?

    $F = ma$. Fundamental equation relating force, mass, and acceleration.

17. What is the formula for weight?

    $W = mg$, where $g$ is the acceleration due to gravity. Weight is the gravitational force on an object's mass.

18. Identify the force responsible for projectile motion.

    Gravity. Only gravity acts after projectile leaves launch point.

19. What is inertia?

    The resistance of an object to change its state of motion. Property of matter described by Newton's first law.

20. What is the relationship between mass and inertia?

    Greater mass implies greater inertia. Mass quantifies inertia; more mass means more resistance to acceleration.

21. State the differences between static and kinetic friction.

    Static friction prevents motion; kinetic friction acts during motion. Static acts before motion; kinetic acts during sliding motion.

22. State the principle of Newton's third law of motion.

    For every action, there is an equal and opposite reaction. Forces always occur in equal magnitude, opposite direction pairs.

23. Identify the direction of the frictional force relative to motion.

    Opposite to the direction of motion. Friction always opposes relative motion between surfaces.

24. What is meant by the term 'action-reaction pair'?

    Two forces equal in magnitude and opposite in direction. Newton's third law pairs acting on different objects simultaneously.

25. State the formula for centripetal force.

    $F_c = \frac{mv^2}{r}$. Required force to maintain circular motion at constant speed.

26. What is the effect of air resistance on falling objects?

    It reduces acceleration due to gravity. Air resistance opposes motion, reducing effective gravitational acceleration.

27. What is the equilibrium condition for a stationary object?

    Net force is zero. Sum of all forces equals zero for objects at rest.

28. What is the normal force?

    A force exerted by a surface perpendicular to the object in contact with it. Reaction force preventing objects from passing through surfaces.

29. In a free-body diagram, how is a force vector represented?

    As an arrow pointing in the direction of the force. Arrow length indicates magnitude, direction shows force direction.

30. What is the gravitational force formula between two masses?

    $F = G\frac{m_1m_2}{r^2}$. Inverse square law for gravitational attraction between masses.

31. State Hooke's Law formula.

    $F = -kx$, where $k$ is the spring constant. Negative sign indicates force opposes displacement direction.

32. Identify the force acting on an object sliding on a frictionless surface.

    No horizontal force; only gravity acts vertically. Without friction, no horizontal forces resist or aid motion.

33. What is meant by an unbalanced force?

    A force that causes a change in the motion of an object. Net force produces acceleration according to Newton's second law.

34. Identify the direction of acceleration in uniform circular motion.

    Towards the center of the circle. Centripetal acceleration always points toward circle's center.

35. State the formula for the gravitational force on an inclined plane.

    $F_g = mg \times \text{sin}(\theta)$. Component of weight parallel to inclined surface.

36. What determines the magnitude of the normal force on an inclined plane?

    Component of weight perpendicular to the surface. Normal force equals weight component perpendicular to surface.

37. State the formula for frictional force.

    $f = \text{μ}N$, where $\text{μ}$ is the coefficient of friction. Friction is proportional to normal force and surface properties.

38. What is the role of the net force in motion analysis?

    It determines the acceleration of an object. Net force directly determines acceleration via Newton's second law.

39. What is the role of a free-body diagram in problem-solving?

    Helps visualize and analyze forces acting on a body. Systematic approach to identify and analyze all forces.

40. What does Hooke's Law describe?

    The force exerted by a spring is proportional to its extension. Linear relationship between applied force and spring deformation.

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