Chapter 7 Exercises: 9, 16, 26, 29, 31, 42

9. When a rifle with a longer barrel is fired, the force of expanding gases acts on the bullet for a longer distance. What effect does this have on the velocity of the emerging bullet? (Do you see why long-range cannons have such long barrels?)

16. A physics instructor demonstrates energy conservation by releasing a heavy pendulum bob, allowing it to swing to and fro. What would happen if, in his exuberance, he gave the bob a slight shove as it left his nose? Explain.

26. Why cannot a Superball released from rest reach its original height when it bounces from a rigid floor?

29. Suppose that you and two classmates are discussing the design of a roller coaster. One classmate says that each summit must be lower than the previous one. Your other classmate says this is nonsense, for as long as the first one is the highest, it doesn't matter what height the others are. What do you say?

31. Does a car burn more gasoline when its lights are turned on? Does the overall consumption of gasoline depend on whether or not the engine is running while the lights are on? Defend your answer.

42. You're on a rooftop and you throw one ball downward to the ground below and another upward. The second ball, after rising, falls and also strikes the ground below. If air resistance can be neglected and if your downward and upward initial speeds are the same, how will the speeds of the balls compare upon striking the ground? (Use the idea of energy conservation to arrive at your answer.)

Chapter 11 Exercises: 3, 4, 16, 19, 20, 30, 34

3. When a container of gas is heated, what happens to the average speed of its molecules?

4. The average speed of a perfume vapor molecule at room temperature may be about 300 m/s, but you'll find the speed at which the scent travels across the room is much less. Why?

16. The atomic masses of two isotopes of cobalt are 59 and 60. (a) What is the number of protons and neutrons in each? (b) What is the number of orbiting electrons in each when the isotopes are electrically neutral?

19. What element results if you add a pair of protons to the nucleus of mercury? (See the periodic table.)

20. What element results if you two protons and two neutrons are ejected from a radium nucleus?

30. The atoms that compose your body are mostly empty space, and structures such as the chair you're sitting on are composed of atoms that are also mostly empty space. So why don't you fall through the chair?

34. Somebody told your friend that if an antimatter alien ever set foot upon the Earth, the whole world would explode into pure radiant energy. Your friend looks to you for verification or refutation of this claim. What do you say?