Please explain in detail! Thank you!! 5 Compare two cases In the first case, and

Question

Please explain in detail! Thank you!!

5 Compare two cases In the first case, and object subject to an unknown external force is sitting motionless on a flat surface In the second case, the same object subject to the same external force is moving across the same surface Which of the following can you say with certainty? A) The frictional force is greater in the second case than in the first case B) The frictional forces are the same in both cases C) The frictional force is greater in the first case than the second case 0) None of these can be said with certainty

Explanation / Answer

According to newtons law :

The net force = acceleration

Fnet= M *a

CASE 1 :

F applied -F friction = M * a (Here a = 0)

F friction = F applied ( eqn 1)

CASE 2 :

F applied -F friction = M * a (Acceleration is there)

So

F friction=F applied - M * a (eqn 2)

From EQNS 1 and 2 we see that F friction is greater in CASE 1

HENCE ANSWER IS 'C'

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