# Homework Help: Flag pole falling

1. Mar 9, 2005

### UrbanXrisis

A ball of mass m is fastened at the end of a flagpole connected to the side of a tall building at point P. The length of the flagpole is l and $$\theta$$ is the angle the flagpole makes with the horizontal. The ball becomes loose and starts to fall. What is the angular momentum of the ball about point P?

so angular momentum is L=mrvsin(theta)

in this problem, the angle between force downwards and the radius is not given, but the angle beween the building and the radius is given. Therefore, sine cannot be used. Cosine must be used for this specific problem.

v=at
v=-gt

$$L=-mlgtCos\theta$$

is this the correct way to approach this question?

2. Mar 10, 2005

### Severian596

I believe your description of this problem is lacking. I picture a ball that's fastened, and when it becomes unfastened it just falls straight down...

3. Mar 10, 2005

### FredGarvin

That's the way I interpreted the question as well. Do you perhaps mean that the flag pole becomes loose and swings down to hit the building? Perhaps then you may be looking for the angular momentum of the ball on the end of the pole...

4. Mar 10, 2005

### Staff: Mentor

I interpreted the problem similarly. Assuming the problem is "What is the angular momentum of the falling ball (with respect to a point on the wall) as a function of time?", then UrbanXrisis's answer is correct. (Maybe he can restate the problem.)