Question

A man walks on a rough surface, the angle between the force of friction and the instantaneous velocity of the person is:

• A. $\pi$
• B. $\pi /2$
• C. $2\pi$
• D. zero

Answer 1

The correct option is D zero

Instantaneous velocity will be in forward direction.

When the man push the ground to move then its the friction which oppose the man from $slipping$ so its the friction which $help$ us to move on ground means the friction is in the direction of motion i.e., in forward direction.

So the angle is $0^0$ means $zero$

Justification-

At smooth surfaces like that if an ice slab, when we push it to move forward our feet slip backward due to lack of forward friction.