Exam 8: Conservation of Energy

A 3.0-kg block is on a horizontal surface.The block is at rest when,at t = 0,a force (magnitude P = 12 N)acting parallel to the surface is applied to the block causing it to accelerate.The coefficient of kinetic friction between the block and the surface is 0.20.At what rate is the force P doing work on the block at t = 2.0 s?

When an automobile moves with constant velocity the power developed is used to overcome the frictional forces exerted by the air and the road.If the power developed in an engine is 50.0 hp,what total frictional force acts on the car at 55 mph (24.6 m/s)? One horsepower equals 746 W.

Starting from rest at t = 0,a 5.0-kg block is pulled across a horizontal surface by a constant horizontal force having a magnitude of 12 N.If the coefficient of friction between the block and the surface is 0.20,at what rate is the 12-N force doing work at t = 5.0 s?

A 3.0-kg block is on a frictionless horizontal surface.The block is at rest when,at t = 0,a force (magnitude P = 2.0 N)acting at an angle of 22° above the horizontal is applied to the block.At what rate is the force P doing work at t = 2.0 s?