1.

During rolling, the force of friction acts in the same direction as the direction of motion of the CM of the body.

Answer»

Solution :(a) False : Frictional force acts OPPOSITE to the direction of motion of centre of mass of a BODY. In the case of rolling, the direction of motion of the centre of mass is backward, hence, frictional force acts in the forward direction.
(b) True : Rolling can be considered as the ROTATION of a body about an axis passing through the POINT of contact of the body with the ground. Hence, its instantaneous speed is zero.
(C ) False : Since body is rolling, it has contripetat force and its instantaneous acceleration is non-zero. So it is false.
(d) True : When perfect rolling begins, the frictional force acting at the lowermost point becomes zero. Hence, work done against friction is also zero.
(e) True : The rolling of a body occurs when a frictional force acts between the body and the surface. The frictional force provides the torque necessary for rolling. In the absence of a frictional force, the body steps from the slope under the effect of own weight.


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