Inertia, momentum 6.4

Transcription

1 6.1

2 6.2

3 6.3

4 Inertia, momentum 6.4

5 Momentum Impulse (Ft) (mv) = F t 6.5

6 6.6

7 6.7

8 6.8

9 6.9

10 -- Questions -- MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 6.10

11 1) A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both move with a combined momentum of A) 1 unit. B) more than 1 unit. C) )less than 1 unit. D) not enough information. 2) When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is A) about 10 times as great. B) more than 1/10 as great. C) less than 1/10 as great. D) about 1/10 as great. 6.11

12 3) A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed? A) 3 m/s B) 4 m/s C) 12 m/s D) 48 m/s E) none of these 4) A car traveling along the highway needs a certain amount of force exerted on it to stop it in a certain distance. More stopping force is required when the car has A) less stopping distance. B) more momentum. C) more mass. D) all of these. E) none of these. 6.12

13 5) Which would be more damaging, driving into a very massive concrete wall with no "give," or having a head-on collision at the same speed with an identical car moving toward you with the same speed? It would be more damaging to hit the A) car. B) wall. C) both the same. 6) A sandbag is motionless in outer space. A second sandbag with 3 times the mass moving at 12 m/s collides with it. They stick together and move at a speed of A) 3 m/s. B) 4 m/s. C) 8 m/s. D) 6 m/s. E) none of these 6.13

14 7) A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at A) 0 m/s. B) 1/2 m/s. C) 1/3 m/s. D) 1/6 m/s. E) 1.5 m/s. 8) Consider massive gliders that slide friction-free along a horizontal air track. Glider A has a mass of 1 kg, a speed of 1 m/s, and collides with Glider B that has a mass of 5 kg and is at rest. If they stick upon collision, their speed after collision will be A) 1/5 m/s. B) 1/6 m/s. C) 1 m/s. D) 1/4 m/s. E) none of these. 6.14

15 9) Which of the following has the largest momentum relative to the Earth? A) a pickup truck speeding along a highway B) a tightrope walker crossing Niagara Falls C) a Mack truck parked in a parking lot D) a dog running down the street E) the Science building on campus 10) A 5000-kg freight car runs into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/s. What was the initial speed of the 5000-kg car? A) 6 m/s B) 4 m/s C) 5 m/s D) 8 m/s E) none of these 6.15

16 11) The conservation of momentum is most closely related to A) Newton's 1st law. B) Newton's 2nd law. C) Newton's 3rd law. 12) Padded d dashboards d in cars are safer in an accident than nonpadded d ones because an occupant hitting the dash has A) increased time of impact. B) decreased impulse. C) decreased impact force. D) a and b above. E) a and c above. 6.16

17 13) The difference between impulse and impact force involves the A) time the force acts. B) difference between acceleration and velocity. C) mass and its effect on resisting a change in momentum. D) distance the force acts. 14) Compared to the force that brings a small car to a stop, the force required to bring a heavy truck traveling at the same speed to a stop A) is less. B) may be less and may be more. C) is more. 6.17

18 15) Two billiard balls having the same mass roll toward each other, each moving at the same speed. What is the combined momentum of the two balls? A) 10 kg m/s. B) 0 kg m/s. C) more information i need to determine. 16) If all people, p animals, trains and trucks all over the world began to walk or run towards the east, then the A) earth would spin a bit faster. B) earth's spin would not be affected at all. C) earth would spin a bit slower. 6.18

19 -- Answers -- MULTIPLE CHOICE. The one alternative that best completes the statement or answers the question. 6.19

20 Chapter 6 1) Answer: A 2) Answer: D 3) Answer: A 4) Answer: D 5) Answer: C 6) Answer: E 7) Answer: C 8) Answer: B 9) Answer: A 10) Answer: A 11) Answer: C 12) Answer: E 13) Answer: A 14) Answer: B 15) Answer: B 16) Answer: C 6.20