A bob of weight 0.1 N hangs from a massless string of length 50 cm. A variable horizontal force which increase from zero is applied to pull the bob until th...

A bob of weight 0.1 N hangs from a massless string of length 50 cm. A variable horizontal force which increase from zero is applied to pull the bob until the string makes an angle of 60o with the vertical. The work done is

Answer Details

Length of the string
L = y + x = 0.5m
∴ x = L - y
= distance moved in the direction of force (which is the weight) when the body is released But cos 60o = y/0.5
∴ y = 0.5cos60 = 0.5 x 1/2 = 0.25
∴ x = l - y = 0.5 - 0.25 = 0.25m
Work done = force x distance moved in the direction of force.
= 0.1 x 0.25 = 0.0252J