A 4.5-kg block slides down a frictionless incline making an angle of 55.0° with the horizontal. (a) What is the total work done on the block when the block slides 1.4 m (measured along the incline)? (b) What is the speed of the block after it has slid 1.2 m if it starts from rest? m/s (c) What is its speed after 1.2 m if it starts with an initial speed of 1.6 m/s? m/s You can use the definition of work as the scalar product of a constant force and displacement to find the work done by each force acting on the block. Then use the work- kinetic energy theorem the find the speed of the block at any given location and for any initial kinetic energy it may have.

(a) A 25 kg child plays on a swing having support ropes that are 2.20 m long. A friend pulls her back until the ropes are 42° from the vertical and releases her from rest. (a) What is the potential energy for the child just as she is released, compared with the potential energy at the bottom of the swing? (b) How fast will she be moving at the bottom of the swing? (c) How much work does the tension in the ropes do as the child swings from the initial position to the bottom?

A skier of mass 61 kg is pulled up a slope by a motor-driven cable. (a) How much work is required to pull him 55 m up a 30° slope (assumed frictionless) at a constant speed of 2.4 m/s? kJ (b) What power (expressed in hp) must a motor have to perform this task? hp

A sled has a total mass of 57 kg and is pushed with a horizontal force from rest. It accelerates at 3.1 m/s? and moves a distance of 93 m on a horizontal surface. The coefficient of kinetic friction between the sled and surface is 0.28. Find the work done by the pushing force. Round your final answer to a whole number.