Equilibrium of concurrent forces, static and kinetic friction, laws of friction, rolling friction - Question Bank

1. Which of the following is a method to reduce friction?
A) Increasing the roughness of surfaces.
B) Using lubricants.
C) Increasing the area of contact.
D) Applying a greater normal force.
2. Consider a body at rest on a rough horizontal surface. If a horizontal force is applied that is less than the limiting friction, the frictional force is:
A) Equal to the applied force and is static friction.
B) Equal to the limiting friction.
C) Zero.
D) Kinetic friction.
3. What is the angle of static friction?
A) The angle at which kinetic friction equals static friction.
B) The angle of inclination at which a body starts to slide down.
C) The angle between the resultant force and the normal reaction.
D) The angle between the applied force and the horizontal.
4. If the angle of inclination of a rough plane is increased such that a body placed on it starts to slide, the angle of inclination is equal to:
A) The angle of kinetic friction
B) The angle of static friction (or angle of repose)
C) The angle of rolling friction
D) 90 degrees
5. Rolling friction is caused by:
A) The interlocking of surface irregularities.
B) The deformation of the rolling body and the surface.
C) The adhesion between the surfaces.
D) The relative motion between the surfaces.
6. Which statement is true regarding the relationship between static and kinetic friction?
A) Static friction is always greater than kinetic friction.
B) Kinetic friction is always greater than static friction.
C) Static and kinetic friction are always equal.
D) Static friction is zero when the object is moving.
7. What is the condition for a body to be in equilibrium under the action of concurrent forces?
A) The resultant force is equal to the weight.
B) The resultant force is equal to the normal reaction.
C) The resultant force is zero.
D) The resultant force is constant.
8. The coefficient of friction depends on:
A) The mass of the object
B) The area of contact
C) The nature of the surfaces in contact
D) The velocity of the object
9. A block of mass 'm' is placed on a rough horizontal surface. If a horizontal force F is applied, and the block starts to move with acceleration 'a', then the force of kinetic friction is:
A) F
B) F - ma
C) ma - F
D) 0
10. When a body is in equilibrium, the net force acting on it is zero. This implies that:
A) The body must be at rest.
B) The body must be moving with constant velocity.
C) The body's acceleration is zero.
D) All of the above
11. Which of the following is a direct consequence of the laws of friction?
A) Objects always move in the direction of applied force.
B) Friction can be completely eliminated.
C) Friction allows objects to start moving.
D) Friction provides grip and stability.
12. The reason why it is difficult to start moving a heavy object is that:
A) Kinetic friction needs to be overcome.
B) Static friction needs to be overcome.
C) Rolling friction is very large.
D) Inertia is very large.
13. If a body is sliding down a rough inclined plane, the friction acting on it is:
A) Static friction
B) Limiting friction
C) Kinetic friction
D) Rolling friction
14. The force of friction is often described as a 'self-adjusting' force. This property is characteristic of:
A) Kinetic friction
B) Rolling friction
C) Static friction
D) Limiting friction
15. When a body is in equilibrium, the algebraic sum of the components of all forces along any direction is:
A) Equal to the magnitude of the resultant force
B) Equal to the magnitude of the net torque
C) Zero
D) Non-zero
16. Which type of friction is responsible for the grip of tires on a road, allowing a car to accelerate and turn?
A) Rolling friction
B) Sliding friction (kinetic friction)
C) Static friction
D) Air resistance
17. If the coefficient of static friction between two surfaces is 0.5, what is the maximum angle of inclination of a plane on which the surfaces can rest without sliding?
A) Approximately 26.57 degrees
B) Approximately 45 degrees
C) Approximately 63.43 degrees
D) 90 degrees
18. What is the direction of the force of static friction when an object is at rest and an external force is applied to cause a tendency of motion?
A) In the direction of the applied force
B) Opposite to the direction of the applied force
C) Perpendicular to the applied force
D) Zero
19. Friction is a:
A) Conservative force
B) Non-conservative force
C) Central force
D) Fundamental force
20. The condition for equilibrium of concurrent forces is often represented by Lami's Theorem, which states that if three concurrent forces P, Q, R acting on a body are in equilibrium, then:
A) P/sin(α) = Q/sin(β) = R/sin(γ)
B) P = Q = R
C) P+Q+R = 0
D) P² + Q² = R²
21. Which scenario best illustrates the concept of limiting friction?
A) A car parked on a slope
B) A book resting on a horizontal table
C) The maximum force you can apply before a stationary object starts sliding
D) A ball rolling down a frictionless ramp
22. Consider a body placed on a rough horizontal surface. If a horizontal force is applied, and the body starts to move, the friction acting on it is:
A) Static friction
B) Limiting friction
C) Kinetic friction
D) Zero
23. Why is it easier to push a heavy box once it starts moving than to get it moving initially?
A) Kinetic friction is greater than static friction.
B) Static friction is greater than kinetic friction.
C) Rolling friction is less than kinetic friction.
D) The mass of the box decreases once it starts moving.
24. The force of friction is proportional to the normal reaction force between the surfaces. This is:
A) Always true for static friction
B) Always true for kinetic friction
C) True for both static and kinetic friction up to the limiting value of static friction
D) True only for rolling friction
25. If a body is in equilibrium, it can be:
A) At rest only
B) Moving with constant velocity only
C) At rest or moving with constant velocity
D) Accelerating
26. Which of the following statements about the coefficient of friction is true?
A) It is always greater than 1.
B) It is always less than 1.
C) It depends on the applied force.
D) It is a dimensionless quantity.
27. Friction that opposes the motion of an object through a fluid (like air or water) is called:
A) Static friction
B) Kinetic friction
C) Rolling friction
D) Fluid friction (or drag)
28. The force required to overcome static friction is generally:
A) Less than the limiting friction
B) Equal to the limiting friction
C) Greater than the limiting friction
D) Independent of the limiting friction
29. When a body is in equilibrium under the influence of three concurrent forces, these forces must be:
A) Parallel to each other
B) Mutually perpendicular
C) Coplanar and their resultant must be zero
D) Equal in magnitude
30. Which of the following is an example of static friction?
A) A sled sliding down a snowy hill
B) A car skidding on ice
C) A person pushing a wall that doesn't move
D) A ball rolling on the ground
31. If a body is in equilibrium, the vector sum of all forces acting on it is:
A) Always positive
B) Always negative
C) Zero
D) Variable
32. The coefficient of kinetic friction (μ_k) is defined as the ratio of:
A) Maximum static friction to the normal reaction
B) Force of kinetic friction to the normal reaction
C) Force of static friction to the applied force
D) Force of rolling friction to the normal reaction
33. A car is moving on a road. The friction between the tires and the road is:
A) Static friction
B) Kinetic friction
C) Rolling friction
D) Not friction at all
34. When an object moves on a rough horizontal surface with a constant velocity, the net force acting on it is:
A) Equal to the force of kinetic friction
B) Equal to the force of static friction
C) Zero
D) Greater than the force of kinetic friction
35. Which of the following is NOT a law of friction?
A) The force of friction opposes the relative motion or tendency of motion.
B) The force of friction is independent of the area of contact.
C) The force of friction is directly proportional to the normal reaction.
D) The force of friction depends on the velocity of the object.
36. The force of friction depends on the nature of the surfaces in contact. This is reflected in the:
A) Normal reaction force
B) Coefficient of friction
C) Applied force
D) Mass of the object
37. If the applied force exceeds the limiting friction, the object will:
A) Remain at rest
B) Start to move
C) Move with decreasing velocity
D) Stop immediately
38. Consider a book resting on a table. If you push the book horizontally with a small force and it doesn't move, the friction acting on the book is:
A) Static friction
B) Kinetic friction
C) Rolling friction
D) Air resistance
39. For concurrent forces acting on a body in equilibrium, the resultant of all these forces must be:
A) Equal to the weight of the body
B) Equal to the normal reaction force
C) Zero
D) Infinite
40. The force of friction between two surfaces in contact is:
A) Always opposite to the direction of motion
B) Always opposite to the direction of applied force
C) Opposite to the direction of relative motion or tendency of relative motion
D) Always perpendicular to the surfaces in contact
41. A block is at rest on an inclined plane. If the angle of inclination is gradually increased, the block will start to slide when the angle reaches a specific value. This value is related to:
A) Coefficient of kinetic friction
B) Coefficient of static friction
C) Coefficient of rolling friction
D) The mass of the block
42. Rolling friction is generally:
A) Greater than kinetic friction
B) Equal to kinetic friction
C) Less than kinetic friction
D) Equal to static friction
43. Which type of friction arises when a body rolls over a surface?
A) Static friction
B) Kinetic friction
C) Rolling friction
D) Limiting friction
44. If an object is at rest on a horizontal surface and a horizontal force is applied, but the object does not move, what can be concluded about the friction acting on it?
A) The friction is kinetic friction and its magnitude is equal to the applied force.
B) The friction is static friction and its magnitude is equal to the applied force.
C) The friction is zero because the object is not moving.
D) The friction is static friction and its magnitude is less than the applied force.
45. The coefficient of static friction (μ_s) is generally related to the coefficient of kinetic friction (μ_k) as:
A) μ_s > μ_k
B) μ_s < μ_k
C) μ_s = μ_k
D) μ_s = 1/μ_k
46. What is the primary characteristic of kinetic friction?
A) It acts when there is no relative motion between surfaces.
B) It acts when there is relative motion between surfaces.
C) It is always greater than static friction.
D) It is independent of the applied force.
47. Which law of friction states that the force of friction is independent of the area of contact between the surfaces?
A) First Law of Friction
B) Second Law of Friction
C) Third Law of Friction
D) Fourth Law of Friction
48. What is the maximum value of static friction called?
A) Limiting friction
B) Kinetic friction
C) Rolling friction
D) Sliding friction
49. Which of the following statements best describes static friction?
A) It opposes motion when an object is already moving.
B) It opposes the tendency of motion when an object is at rest.
C) It is a constant force regardless of the applied force.
D) It is equal to the kinetic friction.
50. What is the condition for an object to be in equilibrium under the action of concurrent forces?
A) The net force acting on the object is zero.
B) The net torque acting on the object is zero.
C) Both the net force and net torque acting on the object are zero.
D) The object is in motion with constant velocity.
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