# How do i do this?

#### ACLerok

how do i do this????!

I'm having trouble with two of my Physics Problems. It goes a little something like this:
A bowling ball weighing w is attached to the ceiling by a rope of length L. The ball is pulled to one side and released; it then swings back and forth as a pendulum. As the rope swings through the vertical, the speed of the bowling ball is v.

What is the acceleration of the bowling ball, in magnitude and direction, at this instant? Take the free fall acceleration to be g.

And then the last:
A bob of mass m is suspended from a fixed point with a massless string of length L (i.e., it is a pendulum). You are to investigate the motion in which the string moves in a cone with half-angle theta.

What tangential speed, v, must the bob have so that it moves in a horizontal circle with the string always making an angle theta from the vertical? Express the speed in terms of m, g, L, and/or theta.

I'm having a particularly hard time with the first one. THanks if you decide to help a brother out!!!

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#### arcnets

Hi ACLerok,
I think these are simple exercises on circular motion and centripetal acceleration.

Maybe the 1st problem confuses you so much because they give some unnecessary information (w and g).
All you need is L and v. Now, what is the centripetal acceleration for a circular motion with radius L, and velocity v? You sure know the formula.

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