# Homework Help: Speed of Flywheel

1. Dec 9, 2007

### bakoo

1. The problem statement, all variables and given/known data

In a hybrid vehicle a flywheel is used to capture the energy of the car during braking. If the car has a total mass of 850kg and the flywheel has a mass-moment of inertia equal to 14kgm2 determine the speed of the flywheel when the car stops for traffic lights in an urban area (you may assume 100% efficiency).

2. Relevant equations

Not sure

I am thinking an equation for Uniform Angular Acceleration.

Or

Centripetal force

I am stuck on what one to use

3. The attempt at a solution

If i can get some hints, i would like to have a stab at this one, i am just 100% lost in Newtons laws and other equations...

2. Dec 9, 2007

### Dick

Think of energy. The kinetic energy of the car has to turn into rotational kinetic energy of the flywheel.

3. Dec 9, 2007

### bakoo

I will post what i have done in a few hours, thanks for the hint...

4. Jul 1, 2008

### zeuso

Hi could you post your results or someone offer some help as i am having problems with the exact same question.

thank you