Rotation 4 Question 2
3. A smooth sphere is moving on a frictionless horizontal plane with angular velocity and centre of mass velocity . It collides elastically and head on with an identical sphere at rest. Neglect friction everywhere. After the collision their angular speeds are and respectively. Then,
(1999, 2M)
(a)
(b)
(c)
(d)
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Answer:
Correct Answer: 3. (c)
Solution:
- Since, it is head on elastic collision between two identical spheres, they will exchange their linear velocities, i.e.,
comes to rest and starts moving with linear velocity . As there is no friction anywhere, torque on both the spheres about their centre of mass is zero and their angular velocities remain unchanged. Therefore,