Answer:
The time is 16 min.
Explanation:
Given that,
Time = 120 sec
We need to calculate the moment of inertia
Using formula of moment of inertia
If the disk had twice the radius and twice the mass
The new moment of inertia
We know,
The torque is
We need to calculate the initial rotation acceleration
Using formula of acceleration
Put the value in to the formula
We need to calculate the new rotation acceleration
Using formula of acceleration
Put the value in to the formula
Rotation speed is same.
We need to calculate the time
Using formula angular velocity
Put the value into the formula
Hence, The time is 16 min.