Physics of Everyday Phenomena W Thomas Griffith Juliet

Physics of Everyday Phenomena W. Thomas Griffith Juliet W. Brosing Chapter 7 Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

Question 7. 1 If the momentum of an object is doubled, its speed must have increased by A) 4 B) 2 C) 0. 5 D) 0. 25

Question 7. 2 An 18 -wheeler and a Volkswagon Beetle are rolling along with the same momentum. Which one is going faster? A) 18 -wheeler B) Volkswagon beetle C) same for both D) impossible to say

Question 7. 3 Maggie drops a stuffed bear over the side of her crib. It hits the floor with speed v and comes to rest. She then drops a rubber ball with the same mass from the same height, and it bounces back upwards with speed v. Compare the change in momentum of the bear and the ball. A) Dpbear = Dpball B) Dpbear = 2 Dpball C) Dpbear = ½ Dpball D) Dpbear = - Dpball

Question 7. 4 An 18 -wheeler and a Volkswagon Beetle are rolling along with the same momentum. If you exert the same force with the brakes to stop each one, which takes a longer time to bring to rest? A) 18 -wheeler B) Volkswagon beetle C) same for both D) impossible to say

Question 7. 5 Red Rover, let Leslie come over. In this childhood game, you try to stop and catch a person who is running directly at you. Who would you rather pick? A) Sean, who weighs 350 N and can run 5 m/s. B) Meihong, who weighs 250 N and can run 8 m/s. C) Deidra, who weighs 300 N and can run 3 m/s.

Question 7. 6 An urban legend has it that the RAF was testing the windshields of their aircraft for bird strikes using a chicken cannon given to them by the USAF. The windshields kept breaking because they were using frozen chickens instead of fresh ones. Using your knowledge of physics, you would reason that the legend is A) false - frozen and thawed chickens have the same momentum on impact. B) true - frozen chickens are harder and come to rest in a shorter time, increasing the force.

Question 7. 7 An astronaut is taking a space walk when his tether breaks. He has a big drill. How can he get back to the space ship? A) Turn his back to the ship and throw the drill forward B) Face the ship and throw the drill forward. C) Throw the drill towards the tether.

Question 7. 8 As a kid playing on the playground, you would bend your knees when you landed after jumping off the monkey bars to reduce the "sting" in your feet. This worked because A) bending your knees gave you upward momentum which partly canceled the downward momentum. B) bending your knees lowered your center of gravity reducing the force of your fall. C) bending your knees increased the time of contact for the ground to bring you to rest. D) you didn't do it on purpose, your knees just buckled.

Question 7. 9 Two forces produce equal impulses, but the second force, F 2, acts for a time twice that of the first force, F 1. Which force, if either, is larger? A) F 1 B) they are the same C) F 2

Question 7. 10 The principle of conservation of momentum A) is valid only for perfectly inelastic collisions B) is valid only for perfectly elastic collisions C) is valid for all collisions D) is valid only if the net external force acting on the system is zero E) states that it is impossible to change the momentum of an object

Question 7. 11 An innocent mosquito is flying along the interstate and has a collision with a speeding semi. Which one feels a greater force? A) The mosquito B) The semi C) They both feel the same force D) There are no forces involved

Question 7. 12 An innocent mosquito is flying along the interstate and has a collision with a speeding semi. Which one experiences a greater change in momentum? A) The mosquito B) The semi C) They both experience the same change in momentum D) There is no change in momentum

Question 7. 13 An innocent mosquito is flying along the interstate and has a collision with a speeding semi. Which one experiences a greater acceleration (change in velocity)? A) The mosquito B) The semi C) They both experience the same acceleration D) There is no change in velocity

Question 7. 14 An collision occurs between object X and object Z. Object X has twice the mass of object Z. Which of the following quantities is NOT the same for the two objects? A) Magnitude of change in momentum B) Magnitude of force felt by each C) Time of collision D) Magnitude of change in velocity

Question 7. 15 These two skaters have just pushed off against one another. One skater has twice the mass as the other. Which one will experience the greater momentum? A) The heavier skater B) The lighter skater C) Neither, they both have the same

Question 7. 16 These two skaters have just pushed off against one another. One skater has twice the mass as the other. Which one will experience the greater velocity? A) The heavier skater B) The lighter skater C) Neither, they both have the same

Question 7. 17 Why is the recoil less if a person holds a gun tightly against the shoulder? A) The recoil is not less. Since momentum is conserved, the recoil is the same whether or not the gun is held tightly B) Your mass becomes part of the system, and since momentum is conserved, the velocity of the gun/person system is reduced C) If the gun is held tightly the bullet doesn’t travel as fast so conservation of momentum leads to a smaller recoil velocity of the gun.

Question 7. 18 An airplane propeller pushes against the air, and the air, by Newton’s 3 rd law, pushes against the propeller. How does a rocket work in outer space where there is no atmosphere? A) There is enough atmosphere, even in outer space, for the same principle to work. B) A rocket exerts a force on its exhaust gases and the gases exert a force on the rocket. C) Rockets use nuclear power and don’t need an atmosphere to work.

Question 7. 19 In which type of collision do the objects stick together afterwards? A) A perfectly elastic collision B) A perfectly inelastic collision C) A partially inelastic collision

Question 7. 20 In which type of collision is no kinetic energy lost? A) B) C) D) A perfectly elastic collision A perfectly inelastic collision A partially inelastic collision Energy is always conserved

Question 7. 21 In which type of collision is the most kinetic energy lost? A) A perfectly elastic collision B) A perfectly inelastic collision C) A partially inelastic collision D) Kinetic energy is always conserved

Question 7. 22 A 280 -lb linebacker running down the field at 7 m/s tackles a 240 -lb halfback running up the field at 9 m/s. Will the halfback gain or lose yards after he is tackled? A) gain B) lose C) neither gain nor lose

Question 7. 23 Wire, briar, limber, lock, three geese in a flock. One flew east, one flew west, and one flew over the cuckoo's nest. If they all flew at the same speed and the cuckoo's nest is to the northwest, which graph represents their total momentum? A) B) C)

Question 7. 24 Two football players moving as shown, collide. Which vector triangle represents their total momentum before the collision? A B C

Question 7. 25 When playing pool or billiards, the paths of the two balls after a collision are at approximately right angles to one another. This is due to: A) The fact that momentum is conserved B) The fact that kinetic energy is conserved C) The fact that both momentum and kinetic energy is conserved

Answer Key to Chapter 7 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) B B C C B B A C A D C C A 14) 15) 16) 17) 18) 19) 20) 21) 22) 23) 24) 25) D C B B A B B C