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**[SOLVED] Angular momentum about a point**

## Homework Statement

A ball having mass m is fastened at the end of a flagpole that is connected to the side of a tall building at point P. The length of the flagpole is l, and it makes an angle of [tex]\theta[/tex] with the horizontal. If the ball becomes loose and starts to fall, determine its angular momentum as a function of time about P. Neglect air resistance.

Note: a diagram is included in my book, so forgive me if the description is vague.

## Homework Equations

[tex]\vec{}L[/tex] = m[tex]\vec{}v[/tex]r

## The Attempt at a Solution

My book gives an answer of -mgltcos[tex]\theta[/tex]k (k being the unit vector for the vertical axis)

I thought that using the equation above, I could use kinematics and insert gt into the equation for v, since it is in free-fall after the ball starts to drop. This leaves me to come up with an expression for r. I'm guessing it must be r = lcos[tex]\theta[/tex], but I'm not sure if this is right. I'm using this to say that the ball will always stay a distance form the wall that is equal to the horizontal component of l initially. Does this sound correct? I am pretty sure it it, but I am not sure if my initial equation for angular momentum is correct for this problem, thanks so much in advance.