Question

When a body rolls without sliding, up an inclined plane, the frictional force is

• A. Directed up the plane
• B. Directed down the plane
• C. Zero
• D. Dependent on its velocity

Answer 1

The correct option is A Directed up the plane

Since the body rolls without sliding,

Tangential acceleration, $a_p$ = 0

and tangential speed, $v_p$ = 0

$\Rightarrow v-r\omega =0\&a-r\alpha$ = 0

$\Rightarrow v=r\omega \&a=r\alpha$

Since the body's acceleration a is downward and parallel to the plane, therefore angular acceleration of the body must be in anticlockwise sense.

That means the friction must act up the plane to produce an anticlockwise torque to produce anticlockwise angular acceleration.

$\therefore$ (A)