Question

A block of mass 2 kg is pulled along a horizontal surface by applying a force at an angle 30º with the horizontal. if the block travels with a uniform velocity and has a displacement 115 cm and the coefficient of friction is 0.15, then the work done by the applied force is

Answer 1

As the block is moving with uniform velocity change in kinetic energy is zero. Therefore the work done by the force applied is the negative of the sum of the work done by the gravitational force and the frictional force. The frictional force is given by 0.15 X MG cos theta which is approximately 2.6 taking acceleration due to gravity at 10 metre per second square. The work done by gravitational force is 0.115 multiplied by MG sin theta which is -1.15J and the work done by frictional force is 2.6 X 0.115 which is -0.299J. Adding up these two we get -1.449 joules. Taking the negative of this we get the work done by the applied force that is 1.449 joules.