What is a good fuel?

A certain car has a fuel efficiency of 25.0 miles per gallon (mi/gal). Express this efficiency in kilometers per liter (km/L).

A pitcher throws a fastball. When the catcher catches it, ___. (4.2) (a) positive work is done (b) negative work is done (c) the net work is zero

KEY TERMS 1. work (4.1) 2. joule 3. foot-pound 4. energy (4.2) 5. kinetic energy 6. potential energy 7. gravitational potential energy 8. conservation of total energy (4.3) 9. conservation of mechanical energy 10. power (4.4) 11. watt 12. horsepower 13. kilowatt-hour 14. alternative energy sources (4.6) 15. renewable energy sources For each of the following items, fill in the number of the appropriate Key Term from the preceding list. o. _____ The ability to do work

Distinguish between what a physicist and a politician might each mean when using the term energy conservation.

Energy is conventionally measured in Calories as well as in joules. One Calorie in nutrition is one kilocalorie, defined as 1 kcal = 4 186 J. Metabolizing 1 g of fat can release 9.00 kcal. A student decides to try to lose weight by exercising. He plans to run up and down the stairs in a football stadium as fast as he can and as many times as necessary. To evaluate the program, suppose he runs up a flight of 80 steps, each 0.150 m high, in 65.0 s. For simplicity, ignore the energy he uses in coming down (which is small). Assume a typical efficiency for human muscles is 20.0%. This statement means that when your body converts 100J from metabolizing fat, 20 J goes into doing mechanical work (here, climbing stairs). The remainder goes into extra internal energy. Assume the students mass is 75.0 kg. (a) How many times must the student run the flight of stairs to lose 1.00 kg of fat? (b) What is his average power output, in watts and in horsepower, as he runs up the stairs? (c) Is this activity in itself a practical way to lose weight?

Energy is conventionally measured in Calories as well as in joules. One Calorie in nutrition is 1 kilocalorie, which we define in Chapter 11 as 1 kcal = 4 186 J. Metabolizing 1 gram of fat can release 9.00 kcal. A student decides to try to lose weight by exercising. She plans to run up and down the stairs in a football stadium as fast as she can and as many times as necessary. Is this in itself a practical way to lose weight? To evaluate the program, suppose she runs up a flight of 80 steps, each 0.150 m high, in 65.0 s. For simplicity, ignore the energy she uses in coming down (which is small). Assume that a typical efficiency for human muscles is 20.0%. This means that when your body converts 100 J from metabolizing fat, 20 J goes into doing mechanical work (here, climbing stairs). The remainder goes into internal energy. Assume the students mass is 50.0 kg. (a) How many times must she run the flight of stairs to lose 1 pound of fat? (b) What is her average power output, in watts and in horsepower, as she is running up the stairs?

KEY TERMS 1. work (4.1) 2. joule 3. foot-pound 4. energy (4.2) 5. kinetic energy 6. potential energy 7. gravitational potential energy 8. conservation of total energy (4.3) 9. conservation of mechanical energy 10. power (4.4) 11. watt 12. horsepower 13. kilowatt-hour 14. alternative energy sources (4.6) 15. renewable energy sources For each of the following items, fill in the number of the appropriate Key Term from the preceding list. n. _____ Time rate of doing work

Work is done on an object when it is ___. (4.1) (a) moved (b) stationary (c) acted on by a balanced force (d) none of the preceding

(Indicates a review question, which means it requires only a basic understanding of the material to answer. Questions without this designation typically require integrating or extending the concepts presented thus far.) 11. Identify as many different ways as you can for giving energy to a basketball.