Assertion and Reason on Friction in Non-Inertial Frame – Rankers Physics

Friction: Practice Problem & Solution

Assertion (A): A block is lying at rest on horizontal rough surface. A person moving with acceleration \(a\) in forward direction will observe a friction force acting on the block. Reason (R): When there is relative motion between the two surface then only static friction acts between them.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Friction. Understanding the underlying formula is key to arriving at the correct answer below:

In an accelerating (non-inertial) frame, a pseudo-force acts on the block, requiring a forward friction force. So, A is true. Static friction acts when there is no relative motion; kinetic friction acts when there is relative motion. Thus, R is false.

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