Ch 10 test study helper

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40 key Chapter Test (page 39) I. Testing Concepts 1–10. Answers will vary. Sample answers are given. 1. Speed is how fast you change position. (1/1) 2. Average speed is the total distance covered divided by the total time it takes. (1/1) 3. Velocity is speed plus a direction. (1/1) 4. Acceleration is how fast your motion is changing. (3/2) 5. When you slow down, you experience a negative acceleration. (4/2)

40 key cont 6. Mass is the amount of matter in an object. (5/3) 7. Inertia is a measure of how much an object resists a change in its motion. (5/3) 8. Momentum is an object’s mass times its velocity. (6/3) 9. Displacement is how far and in what direction an object has moved form its starting point. (1/1) 10. The law of conservation states that when two objects collide, the total momentum before the collision is the same as the total momentum after the collision. (7/3)

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41 key II. Understanding Concepts 1. e (1/1) 2. d (1/1) 3. b (3/2) 6. AB (2/1) 7. BC (2/1) 8. D (2/1) 9. v = d/t = 3km/20 min = 9 km/h (2/1) 10. displacement (1/1) 11. 5 m/s (6/3) 12. mass (5/3) 13. mass and velocity (6/3) 14. are accelerating (3/2)

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42 key III. Applying Concepts 1. A, B, C, E (2/1) 2. B (2/1) 3. D (2/1) 4. F (2/1) 5. The car is slowing down 5 m/s for every second it travels. (2/1) 6. No, it might be changing direction. (4/2)

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43 k 7. a. 10 km + 5 km + 15 km + 5 km = 35 km (1/1) b. 5 km east (1/1) 8. a = (vf –vj)/t = (23 m/s – 30 ms)/3 s = –2.3 m/s2 (4/2) 9. 5 kg (20 m/s ) + 10 kg (5 m/s) = 15 v; v = 10 m/s (7/3)

43 k 1. Your distance would most nearly equal your displacement because you would come closer to moving in a straight line. Your friend would probably go around many curves, so her distance would be a great deal more than her displacement. (1/1) 2. No, you would also need to know the direction in which the storm is moving. You need to know its velocity, not just it speed. (1/1) 3. Inertia is a measure of an object’s resistance to a change in its motion. It is determined by the mass on an object. Momentum is a measure of how hard it is to stop an object. It is calculated by multiplying the mass of the object by its velocity. An object always has inertia. An object has momentum only when it is moving. (5/3) 4. If they have the same velocity, the bowling ball would be much harder to stop because it has greater mass. (7/3) 5. The slow velocity of the massive rocket ship is equal to the rapid velocity of the less massive exhaust gases that are expelled in the opposite direction from the rocket engine. (7/3)

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