Exam 6: Work and Energy

Car drag racing takes place over a distance of a mile (402 m) from a standing start. If a car (mass 1500 kg) could be propelled forward with a pulling force equal to that of gravity, what would be the change in kinetic energy and the terminal speed of the car (in mph) at the end of the race be? (For comparison, a modern, high-performance sports car may reach a terminal speed of just over 100 mph = 44.7 m/s.)

A particle that is subjected to a variable force travels a distance of 20 m in a straight line in the same direction as the force. The force varies as follows: First, 5.0 m and F = 0 Next, 5.0 m and F = 3.0 N Next, 5.0 m and F = 6.0 Last, 5.0 m and F decreases uniformly from 6.0 N to zero What was the total work done by this force during the full 20-m trip?

If mechanical work is done on a body, the body must

An electrical appliance expends energy as shown in the graph. The power developed in the appliance between t = 15 s and t = 25 s is

Use the figure to answer the question. The graph shows the speed of a light truck of mass 4000 kg coasting on neutral down a level straight road. The truck is slowing down due to air resistance and rolling friction. -Estimate the work done per second by the retarding force at t = 5s.

Negative work means

A skier of mass 50 kg is moving at speed 10 m/s at point P₁ down a ski slope with negligible friction. What is the skier's kinetic energy when she is at point P₂, 20 m below P₁?

If a fighter jet doubles its speed, by what factor should the power from the engine change?

The object in the figure has a mass of 3.45 kg and is pulled up a slope AB, which is 36 m long; the height BC is 3.00 m. There is no friction and the acceleration is constant. The speed v₁ at A is 3.5 m/s whereas the speed v₂ at B is 5.5 m/s. The average power developed by the motor pulling the object is

The work-kinetic energy theorem states that

Two forces, both of magnitude 12 N and directed 35 degrees either side of the direction of motion, pull a crate 15 m. How much work is done by the forces in moving the crate?