Posted by Tom on .
A 0.34 kg pendulum bob is attached to a string 1.2 m long. What is the change in the gravitational potential energy of the system as the bob swings from the bottom of the string, where θ = 37°?
i don't know how to do this. The bottom of the string is 1.2 m and it moves 37°...

physics 
Little Miss X,
Use trigonometry to figure out the displacement in the y direction
(1.2 m) * (cos 37) = displacement in the y direction
Displacement in x direction is not a concern here since we are talking about the gravitational force
the gives you delta y
then use you formula for potential energy due to y displacement to get change on gravitaitonal potential energy I think it is force* delta y * mass
mgy = gravitational potential energy
The force in this case is 9.8 (that due to gravity)