A horizontal plane supports a fixed vertical cylinder of radius `R` and a particle is attached to the cylinder by a horizontal thread `AB` as shown in Fig. The particle initially rest on a horizontal plane. A horizontal velocity `v_(0)` is imparted to the particle, normal to the threading during subsequent motion. Point out the false statements:

Options

A. angular momentum of particle about O remains constant
B. angular momentum about B remains constant
C. momentum and kinetic energy both remain constant
D. kinetic energy alone remains constant

Answer

D

Explanation

From the diagram we can see that net torque about O and B is not zero. Therefore angular momentum changes about these points.
As the tension is always perpendicular to velocity therefore work done is zero and sped remains constant and hence the kinetic energy.
But the direction of velocity changes continuously and hence momentum changes.