Question

A rock rests on a level surface. The magnitude of the force on the surface due to the rock is FSR and
the magnitude due to the force on the rock due to the surface is F
[ 1
If we compare these forces we find
a) FR <FRS
b) FSR = Frs
c) FSR > FRS
d) data is insufficient​

Answer 1

Answer:

B

Explanation:

The correct option is (B) FSR = FRS when the rock is at rest but then FSR > FRS.

Consider the rock is on an inclined surface having an angle θ with ground. The magnitude of the force on the surface due to the rock is FSR, and the magnitude of the force on the rock due to the surface is FRS, which is shown in below figure.

Figure:

232-1432_1.PNG.

When the rock is at rest the two forces FSR and FRS will be equal to maintain balance. But when the rock starts to slide down the incline the tangential force FSR Sinθ will dominate upon the force on the rock due to the surface FRS. Therefore if we compare these forces, we find FSR = FRS when the rock is at rest but then FSR> FRS.

From the above observation we conclude that, option (B) is correct.