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**[SOLVED] Angular Momentum**

**1. Homework Statement**

A 4.60 kg counterweight is attached to a light cord, which is wound around a spool (refer to Fig. 10.20). The spool is a uniform solid cylinder of radius 8.00 cm and mass 1.30 kg.

(a) What is the net torque on the system about the point O?

Magnitude

(b) When the counterweight has a speed v, the pulley has an angular speed = v/R. Determine the total angular momentum of the system about O.

(c) Using the fact that = dL/dt and your result from (b), calculate the acceleration of the counterweight.

**2. Homework Equations**

[tex] L = r X P[/tex]

[tex] \tau = r X F[/tex]

[tex] L = I\omega[/tex]

**3. The Attempt at a Solution**

I was able to solve the first part:

[tex] \tau = rF [/tex]

[tex] \tau = (0.08)(4.6)(9.8) = 3.61 Nm[/tex]

I am not sure how to solve part B though, here is what I tried but it was wrong:

[tex] L_{net} = rp + I\omega [/tex]

[tex] L_{net} = r X mv + I*\frac{v}{r} [/tex]

[tex] L_{net} = v (r X m + \frac{I}{r})[/tex]

I factored out the v because it doesn't give you the velocity, and the answer space looks like this:

________ X v kg *m^2/s