# Homework Help: Simple Pendulum bob

1. Dec 15, 2007

### ThenewKid

1. A mass of 500g is used as a pendulum bob so that it forms a pendulum that is 2meters long. The pendulum is displaced from its rest position by an angle of 10 degrees.
A. How high is the pendulum bob above its original position?
B. What is the magnitude of the energy that the pendulum bob possesses in this position?
C. What is the maximum speed of the the pendulum bob when it is released.

2. GPE= Weight x Height mgh
Ke= 1/2mv2
v=squareroot of 2gh
L-Lcos0

3. For A I used the L-Lcos0 equation and got -3.35m. Pretty sure thats wrong.
For B I used GPE=mgh and got 9.8 for the magnitude. Pretty sure this is correct.
For C I used v=squareroot of 2gh and got 6.26m/s as the maximum speed. Positive this is correct.

God, this homecourse really does not give much to go on...jeez.

2. Dec 15, 2007

### malty

Isn't 10 degrees too large of an oscillation for it to be simple pendulum?

3. Dec 15, 2007

### mgb_phys

A you hsve the right idea but have the numbers wrong - draw a diagram
B,C use PE and KE = correct

4. Dec 15, 2007

### Squeezebox

1.A. h= 2m-(cos10*2m)
h=.03m

B. gpe=(.5kg)(9.8m/s^2)(.03m)
GPE=.15J

C. .15J=(.25kg)(v^2)
√(.6)=v
.77m/s=v

5. Dec 15, 2007

### Kurdt

Staff Emeritus
At 10 degrees the value for period is only about one quarter of a percent off the real value.