Problem Solving Practice 1: Work

Practice: Types of Energy

1. A moving car has kinetic energy. If it speeds up until it is going four times as fast, how much kinetic energy does it have in comparison?

2. Find the change in the potential energy of a 10-kg block as it is lowered 0.80 m.

3. How many joules of kinetic energy does a 1.2-kg book have when it is tossed across the room at a speed of 2 m/s?

4. A car is lifted a certain distance in a service station and therefore has potential energy relative to the floor. If it were lifted twice as high, how much potential energy would it have?

5. What is the elastic potential energy in a spring with a spring force constant of 135 N/m when it is stretched 0.2 m?

6. What is the elastic potential energy in a spring with a spring force constant of 15 N/m when it is stretched 0.5 m?

7. What minimum amount of work must the elevator do to lift a 60-kg person from the ground floor to the top floor of a 195-m high apartment building? HINT: The force is the person’s weight.

8. Two cars a lifted to the same elevation in a service station. If one car is twice as massive as the other, how do their potential energies compare?

9. How much work is done on a 75-N bowling ball when you carry it horizontally across a 10-m wide room?

10. Determine the work done by a string on a block as the block is lifted 0.80 m along the incline. The string tension is 50 N. Should this be positive or negative?

11. Dan Jansen of the United States won a speed-skating competition at the 1994 Winter Olympics in Lillehammer, Norway. He did this by skating 500 m with an average speed of 14 m/s. If his mass was 65 kg, what was his kinetic energy?

12. Susie Maroney from Australia set a women’s record in long-distance swimming by swimming 93,625 m in 24.00 h. What was Maroney’s average speed (in m/s)? If Maroney’s mass was 55 kg, what was her kinetic energy?

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