Question

A smooth sphere A is moving on a frictionless horizontal plane with angular speed ω and center of mass velocity v. It collides elastically and head on with an identical sphere B at rest. Neglect friction everywhere. After the collision, their angular speeds are ωA and ωB respectively. Then

• A. ω_B = ω
• B. ω_A< ω_B
• C. ω_A = ω
• D. ω_A = ω_B

Answer 1

The correct option is C

ω_A = ω

Since there is no friction between the sphere and horizontal surface and also between the spheres themselves, there will be no transfer of angular momentum from sphere A to sphere B due to collision.Since the collision is elastic and the spheres have same mass,the sphere A only transfers its linear velocity v to the sphere B.Sphere A will continue to rotate with the same angular speed ω at a fixed location.