Question

A student initially stands on a circular platform that is free to rotate without friction about its center. The student jumps off tangentially, setting the platform spinning. Quantities that are conserved for the student-platform system as the student jumps include with of the following?

I. Angular momentum
II. Linear momentum
III. Kinetic energy

Answer 1

I. Angular Momentum

Step-by-step explanation:

We are given that the system is the student-platform system.

When the student jumps off tangentionally, the system no longer is a closed system and thus external forces (like gravity) may act on the student and thus linear momentum will not be conserved.

Meanwhile, Kinetic Energy will also not be conserved as the system moves to an open system because of external work from gravity.

However, angular momentum will only change if there is external torque: in this case, there is no external torque.

I hope this helped!

Answer 2

I. Angular momentum

Step-by-step explanation:

As we know that rate of change of angular momentum is known as torque.

So we can say that

`T=(dL)/(dT)`

T= Torque

L=Angular momentum

When there is no any toque then T= 0

`T=(dL)/(dT)`

`(dL)/(dT)=0`

So we can say that angular momentum is constant.

In the given problem ,the external torque is zero then the angular momentum of the system will be conserved .

The system have some backward reaction force like axle or pivot that is why the kinetic and linear momentum will not be conserved .