A pendulum bob of mass 0.5kg hanging from a vertical string of length 20m attached to a fixed point is pulled to one side with the string taut until it makes an angle 30° to the vertical. Calculate the work done on the bob?
1 Answer
Mar 16, 2018
Using Law of conservation of energy and assuming that pendulum is ideal and no energy is lost in friction,
Work done on the bob
#=# Increase in potential Energy of bob
Increase in potential Energy of bob
#=mgDeltah#
where#m# is mass of bob,#g=9.81\ ms^-2# is acceleration due to gravity and#Deltah# is change in height of bob.
As shown in the figure,
Work done on the bob
#=0.5xx9.81(20-20\ cos30^@)#
#=># Work done on the bob#=0.5xx9.81xx20(1- sqrt3/2)=13.1\ J#
