Answer 2_5_2
A horse is pulling a barge along a canal as shown in the diagram. It pulls the barge with a force of 1000 N a distance of 75 m. The angle the rope is at 15o to the direction of travel.
The situation is shown in the diagram:
(a) Can you explain why the answer is NOT 75000 J?
The line of action of the force is not in the same direction as the movement. So we need the horizontal (or more correctly) forward component of the force.
(b) What is the work done by the horse?
W = Fs cos q = 1000 N x 75 m x cos 15 = 1000 N x 75 m x 0.966 = 72 400 J