How Much of a Bicycle's Kinetic Energy is in Its Wheels?

[jjf5122]

Homework Statement

A bicycle weighs 23lbf, including hollow wheels each weighing 2.5lbf. Calculate how much of the bike's kinetic energy is in the wheels. Ans = 36%

Homework Equations

1. I = mr^2 <----- i think this is 2mr^2 because of two wheels
2. Kinetic Energy = 1/2mv^2 <---- translational of the bike
3. Ke = I(omega)^2 <------ rotational of the wheels
4. Ktotal = 1/2mv^2 + Iw^2

The Attempt at a Solution

I tried putting the rotational kinetic energy over the total kinetic then multiplying by 100 but it isn't working... Also I am not sure if I am supposed to double the rotational energy or not. I think that I am only supposed to double the inertia. Either way i can't seem to arrive at the given solution. Am i doing something wrong?

 

[denverdoc]

The wheels carry energy in two ways as you suggest. I would think then it would be 2*(1/2mv^2+Mr^2)/ (the translational kinetic energy plus the rotational of the whole bike)--perhaps you neglected the latter term in your calculation?