Angular Momentum (pendulum) Help

1. Feb 13, 2012

tdub96

1. The problem statement, all variables and given/known data
a 1.5 kg pendulum bob swings in a vertical circle at the end of a 2m long string with negligible weight. If the bob is dropped from a height in which the string is horizontal and taut, what is the angular momentum at the bob's lowest point (in kgm/s^2)?

a 40
b 10
c 30
d 20
e 50

2. Relevant equations
L=Iw
L=mrv
L(initial)=L(final)

3. The attempt at a solution
I tried using the formula v2=vo2+2aΔy to solve for linear velocity first. It would be v= sqrt(2*9.8m/s/s*2m) because it falls the length of the string to reach the horizontal correct? From there, I calculated v to be 6.26m/s, and then subbed that into L=mrv for a final answer of 18.78kgm2/s, but its a bit off the possible choices and I'm skeptical of my work.

Any help would be greatly appreciated!

2. Feb 13, 2012

fluidistic

Looks ok to me. Maybe they took g as 10 m/s² which should be a slightly greater velocity and hence angular momentum.

3. Feb 13, 2012

tdub96

Using 10m/s/s comes out to be 18.97, which is closer, but Im still not confident in that. I'm gonna keep trying some stuff, if anyone has anything to contribute please do so!