Chapter 4 Exercises: 3, 8, 25, 28, 34, 57

3. Is it possible to go around a curve in the absence of a force? Defend your answer.

8. A 400-kg bear grasping a vertical tree slides down at constant velocity. What is the friction force that acts on the bear?

25. A racecar travels along a raceway at a constant velocity of 200 km/h. What horizontal forces act and what is the net force acting on the car?.

28. Free fall is motion in which gravity is the only force acting. (a) Is a sky diver who has reached terminal speed in free fall? (b) Is a satellite circling the Earth above the atmosphere in free fall?

34. What is the acceleration of a rock at the top of its trajectory when thrown straight upward? (Is your answer consistent with Newton's second law?)

57. If you drop a pair of tennis balls simultaneously from the top of a building, they will strike the ground at the same time. If you fill one of the balls with lead pellets and then drop them together, which one will hit the ground first? Which one will experience greater air resistance? Defend your answers.
Chapter 5 Exercises: 4, 18, 23, 24

4. For each of the following interactions, identify action and reaction forces. (a) A hammer hits a nail. (b) Earth gravity pulls down on a book. (c) A helicopter blade pushes air downward.

18. Why does a rope climber pull downward on the rope to move upward?

23. Suppose two carts, one twice as massive as the other, fly apart when the compressed spring that joins them is released. How fast does the heavier cart roll compared with the lighter cart?
24. If a Mack truck and Honda Civic have a head-on collision, upon which vehicle is the impact force greater? Which vehicle experiences the greater acceleration? Explain your answers.