Assertion (A): The coefficient of kinetic friction is always strictly less than the coefficient of limiting static friction. Reason (R): Once motion starts, the inertia of rest is broken and interlocking of surface irregularities is less effective. MCQ with Answer and Explanation

Question Report Error

Assertion (A): The coefficient of kinetic friction is always strictly less than the coefficient of limiting static friction. Reason (R): Once motion starts, the inertia of rest is broken and interlocking of surface irregularities is less effective.

A. Both A and R are true and R is the correct explanation of A.

B. A is true but R is false.

C. Both A and R are true but R is NOT the correct explanation of A.

D. A is false but R is true.

Answer: Option A

Solution (By JKExamLibrary)

Static friction opposes impending motion, reaching a maximum called limiting friction. Once the object moves, it doesn't have enough time for the microscopic irregularities (asperities) of the two surfaces to interlock strongly. Thus, the force required to keep it moving (kinetic friction) is slightly less than the force required to start the motion.

This question belongs to: Science Physics

Discuss this Question (0)

No comments yet. Be the first to start the discussion!

Practice More Physics Questions

Question #1 Report Error

A constant force acting on a body of mass 5 kg changes its speed from 2 m/s to 8 m/s in 10 s. The magnitude of force is

A. 5 N

B. 0.5 N

C. 3 N

D. 1 N

View Answer & Solution Discuss

Correct Answer: Option C

Explanation:
Acceleration a = (v-u)/t = (8-2)/10 = 0.6 m/s². Force F = m×a = 5 × 0.6 = 3 N. Alternatively, impulse = change in momentum = 5×(8-2) = 30 kg m/s, time = 10 s, so average force = 30/10 = 3 N. Always check direction, but magnitude is 3 N.

This question belongs to: Science Physics