Question

A 0.33 kg pendulum bob is attached to a 1.2 m string. What is the change in the gravitational potential energy of the system as the bob swings

Answer 1

L = 1.2 meter
m = 0.33 kg
depends how far it swings
if it swings at angle c from vertical
rise from bottom = L (1 - cos c)
so increase in Pe = m g h = m g L(1- cos c)
if c is a small angle then cos c = 1 - c^2/2 ..... etc series...
then
Pe = m g L (c^2/2)
I suspect you know how to get c(t) for a pendulum if you know the magnitude of the swing angle