As a ball rolls down the inclined plane, the power of gravitational force Pg and frictional force Pf thereafter :

Question

(1)	Pg increases with time and Pf remains constant with time.
(2)	Pg as well as Pf remain constant with time.
(3)	Pg as well as Pf increase with time.
(4)	Pg remains constant and Pf decreases with time.

Answer 1

when the ball rolls down the inclined plane then there will be two forces,

 Gravitational force & Friction force ,

For a body to purely roll down the inclined plane, static friction will act at the contact point and the will not slip on the surface. Hence work done by friction force is zero but due to gravitational force work done will be mgh 

As Power = (work done)/ total time.

So, (a) is correct.