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ZzZerozZ

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## Homework Statement

Flywheels are large, massive wheels used to store energy. They can be spun up slowly, then the wheel's energy can be released quickly to accomplish a task that demands high power. An industrial flywheel has a 1.5m diameter and a mass of 270kg . Its maximum angular velocity is 1200rmp .

a)A motor spins up the flywheel with a constant torque of 53Nm . How long does it take the flywheel to reach top speed?

Ans:180s

b) How much energy is stored in the flywheel?

Ans:6*10^5 J

c) The flywheel is disconnected from the motor and connected to a machine to which it will deliver energy. Half the energy stored in the flywheel is delivered in 2.5s . What is the average power delivered to the machine?

Ans:120000Watt

MY QUESTION IS:

**d)How much torque does the flywheel exert on the machine?**

## Homework Equations

k=0.5*Iw^2

torque=F*r=Ialpha

P=F*v

## The Attempt at a Solution

I try to solve with 2.5x120000= 0.5*Iw^2 then use w to find alpha and finally solve for the

Torque, but my answer is wrong... Can anyone gve me a hint??