A wagon wheel and inertia

[envscigrl]

A wagon wheel 1.00m in diameter consists of a thin rim having a mass of 7.25kg and six spokes each having a mass of 1.30kg. Determine the moment of inertia of the wagon wheel for rotation about its axis.

I thought that I could simply sum the masses (7 of them) and the multiply them by them by the radius squred. Didnt work!

I am having some problems with this chaper on rotational dynamics and torque. If anyone knows of any really good books or websites that could be helpful please let me know. Thanks!

[Tide]

You cannot simply multiply the masses by the square of the radius to find their moment of inertia. Calculate (by integration) or look up the moment of inertia of a thin rod then apply the parallel axis theorem for moments.