Question

A 0.2 kg ball is suspended from a thread of 1m. it is pulled at an angle o 30 degree with the vertical. calculate the work done against gravity

Answer 1

Here,
θ = 30°
L = 1 m
m = 0.2 kg
g = 10 ms-2

Work done is stored as PE in the bob. 

PE = mgh
  = 0.2×10×1×(1 – cos300)
  = 0.2×10×(1 – 0.87)
  = 0.26 J