Assertion (A): When the disc rolls without slipping, friction is required because condition of pure rolling is velocity of point of contact is zero.
Reason (R): The force of friction in the case of a disc rolling without slipping down an inclined plane is zero.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true: For pure rolling, the point of contact velocity is zero, and friction provides the necessary torque.
Reason (R) is false: For a disc rolling without slipping down an inclined plane, friction is present and acts up the incline to provide the torque for rotation. Thus, (A) is true, (R) is false.
Assertion (A): A body is rolling without slipping on a surface. There must be frictional force to start such a motion.
Reason (R): In rolling without slipping, work done against the frictional force is zero on rolling body.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true: Friction provides the necessary torque to initiate the angular acceleration required for rolling.
Reason (R) is true: In pure rolling, the point of contact is instantaneously at rest, so the work done by static friction is zero. Both statements are true, but R does not explain A.
Assertion (A): A wheel moving down a perfectly frictionless inclined plane will undergo slipping (not rolling).
Reason (R): For pure rolling, work done against frictional force is zero.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true; friction provides the torque for rolling. Without friction, the wheel slips. Reason (R) is true; in pure rolling, the contact point is stationary, so static friction does no work. However, (R) does not explain (A).