A force F is used to raise a 4-kg mass M from the ground to a height of 5 m. What is the work done by the force F ? (Note : sin600=0.87;cos600=0.50  Ignore friction and the weights of the pulleys)

Work is the product of force and distance. The easiest way to calculate the work in this pulley problem is to multiply the net force or the weight mg by the distance it is raised; 4kg×10m/s2×5m=200J .