# Homework Help: Pendulums with Mechanical Energy (conical pendulum?)

1. Jul 22, 2011

### victoration1

1. The problem statement, all variables and given/known data

The pendulum bob in Figure 6.11 must circle
the rod interrupting its swing, and the string
must remain taut at the top of the swing. How
far up must the bob be raised before releasing
it to accomplish these goals?

2. Relevant equations

Potential Energy = mgh
Kinetic Energy = 1/2mv^2
mgh = 1/2mv^2

3. The attempt at a solution

I'm still unclear with what the question is asking for or how I'm suppose to solve it; though I'm guessing it deals with the conversion of kinetic energy into gravitational potential energy and maximum height. How the rod play into the question, or what the distance from the rod to the pendulum bob means, I've no idea. This sounds awfully similar to a conical pendulum, which a quick wikipedia search showed as pretty complicated.
So, how do?

2. Jul 22, 2011

### Dick

When the string hits the rod, it the bob will start circling the rod in a 10 cm radius circle. It won't reach the point 10 cm above the rod unless you release it from high enough. How high is 'high enough'?

3. Jul 26, 2012

### nazz80

Here is the Solution for you: Please click on the image. For more questions plz send requests here....

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