A heavy solid disk rotating freely and slowed only by friction applied at its outer edge takes 120 seconds to come to a stop.
If the disk had twice the radius and twice the mass, but the frictional force remained the same, the time it would it take the wheel to come to a stop from the same initial rotational speed is .

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.