Text questions that are similar to the ones below:
CQ 4.3, 4.17, 4.19
P 4.1, 4.2, 4.14, 4.15, 4.20, 4.25
Conceptual Questions:
1. In the motion picture It Happened One Night, Clark Gable and Claudette Colbert are in a bus. Mr. Gable is standing in front of Ms. Colbert, who is seated. The bus suddenly starts moving forward and Mr. Gable falls in Ms. Colbert's lap. Why did it happen (physics, not the whim of the director)? (Sort of like CQ-4.3)
2. If there is an equal and opposite force for all forces, why is there ever any acceleration? (CQ-4.17)
3. Define normal force. (CQ-4.19)
Numerical (mostly) Problems:
1. A 7 kg bowling ball experiences a net force of 5 N. What will be its acceleration? (P-4.2)
ans: 0.71 m/s2
2. Rita accelerates a 0.4 kg ball from rest to 9 m/s during the 0.15 s in which her foot is in contact with the ball. What average force does she apply to the ball during the kick? (P-4.1, but need to calculate acceleration).
ans: 24 N
3. A 70-kg man jumps 1 m down onto a concrete walkway. His downward motion stops in 0.02 seconds. If he forgets to bend his knees, what force is transmitted to his leg bones? Don't forget to include his weight in the problem. (P-4.1 and P-4.14, but need to calculate acceleration).
4. A freight train consists of two 80,000 kg engines and 45 box cars of 55,000 kg each. The train accelerates at 0.05 m/s2. Each car suffers 16,000 N friction. What then are the forces in the coupling between the 37th and 38th car? (P-4.15)
ans: 1.5x105 N forward on car 38 and backward on car 37.
5. The accelerating force of the wind on a small 200 kg sailboat is 707 N northeast. If the drag of the keel is 500 N acting west, what is the acceleration (value and direction) of the boat? (P-4.20 without friction)
ans: 2.5 m/s2 due North
6. Acceleration due to gravity on the moon's surface is 1/6th that on Earth. An astronaut's life support backpack weighs 300 lb on Earth. What does it weigh on the moon? (P-4.25)
ans: 50 lb