Question

A particle is confined to rotate in a circular path decreasing linear speed, which of the following is correct?

• A. $\overrightarrow{L}$ (angular momentum) is conserved about the centre
• B. Only direction of angular momentum $\overrightarrow{L}$ is conserved
• C. It spirals towards the centre
• D. Its acceleration is towards the centre

Answer 1

The correct option is B Only direction of angular momentum $\overrightarrow{L}$ is conserved

$|\overrightarrow{L}|=mvr.$ Since v is changing (decreasing), L is not conserved in magnitude. Since it is given that a particle is confined to rotate in a circular path, it cannot have a spiral path. Since the particle has two accelerations $a_{c}and{a}_t,$ therefore the net acceleration is not towards the centre.

The directions of $\overrightarrow{L}$ remains the same even when the speed decreases.