Angular Momentum Horizontal Metallic Bob

[RivalDestiny]

Homework Statement

A small metallic bob is suspended from the
ceiling by a thread of negligible mass. The
ball is then set in motion in a horizontal circle
so that the thread describes a cone. Calculate
the magnitude of the angular momentum of the
bob about a vertical axisthrough the supporting point.

angle: 29
string length: 2.4 m
mass: 9 kg

Homework Equations

L= r x mv

The Attempt at a Solution

mass is given in the problem

radius can be found by:

(string length) * sin29 = r

I don't know how to find the velocity...do we first have to find the angular velocity and convert that over to linear velocity?

 

[Dick]

You have to draw a force diagram on the bob. It has a force of mg pointing down. There is a tension force T directed along the string. The vertical components of those two forces must cancel. That leaves you with a horizontal component of T pointing towards the center of the circle it's rotating in. Using F=ma that you can find the acceleration of bob towards the center of the circle. Equate that to the acceleration you produced by the circular motion.

 

[RivalDestiny]

alright, so I found the centripetal acceleration. Would I equate that to:

a=v^2/r?

r being the (L)*sin29..

then that would be v?