A boy of weight 400 N is moving on a straight level road against a frictional forceof 6 N.After travelling a distance of 1.4 kmhe forgot the correct path at a

Question

A boy of weight 400 N is moving on
a straight level road against a frictional forceof 6 N. After travelling a distance of 1.4 kmhe forgot the correct path at a round aboutof radius 100 m. However, he moves on thecircular path for one and half cycle and thenhe moves forward upto 1.4 km. Find the network done by the boy against the frictionalforce.

Answer 1

So net work is force times distance.  You know the force of friction (6 N), so you just have to add up the distances, which sounds like two straight line distances of 1400 m and 1.5 times around a circle of radius 100.  So,

 

D = 2(1400) + 1.5 * 2 * π * 100

 

After you evaluate that, you'll multiply by 6N to get the work done by friction, which is the same as the work done by the boy against friction.