1. Define work and energy.  Differentiate between kinetic and potential energy.
2. Calculate the kinetic energy, gravitational potential energy, and spring potential energy of an object.
3. Define the conservation of energy principle and use it to solve physical problems.
4. Define power and differentiate between it and energy.

Conceptual Questions

1. When a golfer hits a golf ball, is he doing work on the ball while his club is in contact with it? Is he doing work on the ball after it loses contact with his club? Are any forces doing work on the ball while it is in flight?
2. Can the kinetic energy of an object be negative?
3. Can the speed of an object change if the net work done on it is zero?
4. Can the gravitational potential energy of an object ever be negative? Explain.

Problems

1. A tugboat exerts a constant force of 5.00 x 10³ N on a ship moving at constant speed through a harbor. How much work does the tugboat do on the ship if each moves a distance of 3.00 km?
2. A horizontal force of 150 N is used to push a 40.0 kg packing crate a distance of 6.00 m on a rough horizontal surface. If the crate moves at constant speed, find (a) the work done by the force and (b) the coefficient of kinetic friction.
3. A 2.0 gm bullet leaves the barrel of a gun at a speed of 300 m/s. (a) Find its kinetic energy. (b) Find the average force exerted on the bullet by the by the expanding gases as the bullet moves the length of the 50 cm long barrel.
4. A 50 kg pole-vaulter running at 10 m/s jumps over the bar. Assuming that her horizontal component of velocity over the bar is 1.0 m/s, and neglecting air resistance, how high did she jump?
5. A 1.50 x 10³ kg car accelerates uniformly from rest to 10.0 m/s in 3.00 s. Find (a) the work done on the car in this time interval, (b) the average power delivered by the engine in this time interval, and (c) the instantaneous power delivered by the engine at t = 2.00 s.

Solutions