Question

Assertion: The value of dynamic friction is less than the limiting friction.
Reason: Once the motion has started, the inertia of rest has overcome.
A. Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.
C. Assertion is correct, but Reason is incorrect
D. Assertion is incorrect, but Reason is correct

Answer 1

Hint: Dynamic friction, also known as kinetic friction, is the friction that resists two relative body motions where kinetic friction is the force acting between two surfaces. Dynamic friction is also classified as Sliding friction, Rolling friction, and Pivot friction.
Here in this question, we need to check both the given statements in Assertion and Reason and comment whether they are both true or not and also whether they are dependent on each other or not.

Complete step by step solution:
Limiting friction is the maximum friction that can be generated between two static surfaces in contact with each other. Once the force is applied between two surfaces, which are greater than its limiting friction, then the motion will occur where force is dependent upon the nature of the surface. Limiting friction is directly dependent upon the magnitude of normal reaction N between two surfaces in contact.
Limiting friction is the maximum value of kinetic friction, i.e., a force is required to move a body, and if friction is adding between two surfaces of contact, then more force is required; hence a large force is required to break the interlocking between the surfaces and if the body starts to move then less force is required to move the body from friction. Hence we can say dynamic friction is less than the limiting friction since more force is required in case of limiting friction to move the body.

So option A. is correct
Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.

Note: Candidates should not get confused that when the body is in motion, there will be no friction at all; however, there will be friction but is less than the static friction.