1. A 55-kg crate is pulled 7.0 m across the floor by a force F whose magnitude is 160 N. The force F is parallel to the displacement of the box. The coefficient of kinetic friction is 0.25. Determine the work done on the crate by each of the four forces that act on the box. Be sure to include the proper plus or minus sign for the work done by each force. Does the crate speed up, slow down, or move with a constant speed?
2. A 7420-kg satellite has an elliptical orbit. The point on the orbit that is farthest from the earth is called the apogee (the far right side of the figure), and the closest point is called the perigee (the left side of the drawing). Suppose that the speed of the satellite is 2820 m/s at the apogee and 8450 m/s at the perigee. Find the work done by the gravitational force when the satellite moves from (a) the apogee to the perigee and (b) the perigee to the apogee.
3. A semitrailer is coasting downhill along a mountain highway when its brakes fail. The driver pulls onto a runaway-truck ramp that is inclined at an angle of 14.0 above the horizontal. The semitrailer coasts to a stop after traveling 154 m along the ramp. What was the truck's initial speed? Neglect air resistance and friction.
4. In the sport of skeleton a participant slides down an icy track, belly down and head first. In the 2010 Winter Olympics, the track had sixteen turns and dropped 126 m in elevation from top to bottom. (a) In the absence of non-conservative forces, such as friction and air resistance, what would be the speed of a rider at the bottom of the track? Assume that the speed at the beginning of the run is relatively small and can be ignored. (b) In reality, the gold-medal winner (Canadian Jon Montgomery) reached the bottom in one run with a speed of 40.5 m/s (about 91 mi/h). How much work was done on him and his sled (assuming a total mass of 118 kg) by non-conservative forces during this run?
5. The figure shows a 0.41-kg block sliding from A to B along a frictionless surface. When the block reaches B, it continues to slide along the horizontal surface BC where the kinetic frictional force acts. As a result, the block slows down, coming to rest at C. The kinetic energy of the block at A is 37 J, and the heights of A and B are 12.0 and 7.0 m above the ground, respectively. (a) What is the value of the kinetic energy of the block when it reaches B? (b) How much work does the kinetic frictional force do during the BC segment of the trip?
