# Change in gravitional potential energy at an angle?

1. Nov 4, 2008

### flemj

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

A 0.23kg pendulum bob is attached to a string 1.2 long at an angle of 30 degrees. What is the change in the gravitational potential energy of the system as the bob swings from point A to point B
U=
2. Relevant equations

.5 mv^2 = mgl
U=E+K

3. The attempt at a solution

in the picture it looks like a string attached to a roof with the ball at rest touching the roof and swinging down to a position 35 degrees below im just not sure how you use the angle of 35 in the problem

2. Nov 4, 2008

### Hootenanny

Staff Emeritus
Can you relate the change in angle to the change in height of the bob?

3. Nov 4, 2008

### flemj

the height isnt given its just the length of the string sorry.

4. Nov 4, 2008

### Hootenanny

Staff Emeritus
I know it isn't given, what I was saying is can you work it out using the angle and the length of the string?

5. Nov 4, 2008

### flemj

would you do that my x sin theta ?

im just really frustrated with this question

6. Nov 4, 2008

### Hootenanny

Staff Emeritus
I'm not sure what my is meant to be, but yes you should use trigonometry.