# Simple Pendulum - Maximum Speed

1. Apr 13, 2010

### mparsons06

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

A simple pendulum has a mass of 0.25 kg and a length of 1.0 m. It is displaced through an angle of 5.0° and then released.

1. What is the maximum speed?

2. What is the maximum angular acceleration?

3. What is the maximum restoring force?

2. The attempt at a solution:

I got numbers 2 and 3 right, but I can't figure out number 1.

Here's my attempt:

m*g*L*sin $$\theta$$ = 1/2 *m*v2
(0.250)*(9.81)*(1.0)*(sin 5) = 1/2 * (0.250)*v2
0.124 = (0.125)v2
v2 = 1.712 = 1.31 m/s

It is incorrect. Can someone please help me as to where I went wrong?

Last edited: Apr 13, 2010
2. Apr 13, 2010

### rock.freak667

You are equating a force to energy.

First draw a free body diagram and find the potential energy when it is displaced at 5°.

3. Apr 13, 2010

### mparsons06

I drew the diagram, but I'm not sure how to find the potential energy?

4. Apr 14, 2010

### rock.freak667

From the lowest point to where it is displaced, what is the vertical height?