Chapter 11 review


    Quantitative problems
      Section 11.1
      1. What is the change in momentum for a 5,000 kg ship in outer space that experiences no net force over a 1 hr period?
      2. A constant net force of 20 N is applied to a 32 kg car, causing it to speed up from 4.0 to 9.0 m/s. How long is the force applied?
      3. A golfer tees up a 45 gram golf ball and hits it with her driver. The club head is in contact with the ball for 9.0 milliseconds (ms), and the velocity of the ball immediately after impact is 79 m/s.
        1. What is the impulse on the ball?
        2. What is the impulse on the club head due to the collision?
        3. What was the average force on the ball during the collision?
      4. Easy Calculate the momentum of a 75 kg person running at 10 m/s.
      5. Easy Calculate the momentum of a jet moving at 700 mph with a mass of 20,000 kg.
      6. Easy Calculate the magnitude of the change in momentum in each of the following examples.
        1. A 1,200 kg car accelerates from rest to a speed of 20 m/s.
        2. A 75 g pellet moving at 18.0 m/s hits a tree and lodges in it.
        3. A 250 g rubber ball hits the floor at 10.0 m/s and rebounds at 6.0 m/s.
        4. A 60 kg student jogging at 3.0 m/s speeds up to 6.5 m/s.
      7. Easy A green ball with a mass of 10.0 kg is heading due east at 50 m/s. A red ball with a mass of 25 kg is heading due west at 15 m/s. Calculate the total momentum of this system.
      8. Medium Which moves faster after being accelerated from rest, (a) a 500 kg boat that has been imparted with a 10,000 N s impulse or (b) a 780 kg boat imparted with a 14,000 N s impulse?
      9. Medium Consider two bowling balls, each with a mass of 4.0 kg. The red ball is moving east at 2.0 m/s. The blue ball is moving west at 1.0 m/s. Calculate the total momentum of the system.
      10. Medium A 1.5 kg tennis ball is slammed by a player who changes its direction by 180°, keeping its speed of 30 m/s the same. What impulse is required to redirect the ball?
      1. Medium A wind-up toy car has a mass of 66 g. The car is wound, and then released, going from being at rest to a constant velocity of 0.8 m/s. If the internal force of the winding on the tires is 0.1 N, what is the duration of the impulse imparted by the winding on the car.
      2. Medium A baseball player hits a 2 kg ball that is approaching with a velocity of 45 m/s. After making contact with the bat, the ball has a velocity of 40 m/s in the opposite direction. Seconds later, the ball is caught by an outfielder. Who imparts a greater impulse on the ball, the batter or the outfielder?
      3. Medium A 100 kg stunt woman falls from a three-story building that is 9.9 m high. If she falls into a net, which slows her down over the course of 1 s, what force did she experience while landing?
      4. Medium A train moves at 40 m/s heading due west. A young child with a mass of 20 kg, disregarding safety, is running down the hallway of the train opposite to the direction of travel, at 4 m/s. What momentum does the child have relative to an observer on the ground? The train has a mass of 100,000 kg.
      5. Medium An impulse J is applied to a ball that is initially at rest, giving it a resulting momentum p1 and kinetic energy Ek1.
        1. If the impulse is doubled to 2J, what is the resulting momentum p2?
        2. If the impulse is doubled to 2J, what is the resulting kinetic energy Ek2?
      Section 11.2
      1. Medium A 3,000 kg truck is traveling 28 m/s through a rainstorm. At the end of its journey, it has collected 500 kg of water and is now moving 24 m/s. Was momentum conserved?
      2. Challenging A 15,000 kg rocket traveling at +230 m/s turns on its engines. Over a 6.0 s period it burns 1,000 kg of fuel. An observer on the ground measures the velocity of the expelled gases to be −1,200 m/s.
        1. What is the resulting speed of the rocket after the burn?
        2. What is the acceleration of the rocket during the burn? Express your answer in meters per second squared and in “g”s.
        3. What impulse is applied to the rocket?
      3. Easy A car and an attached trailer have a combined mass of 3,000 kg. The car and trailer are moving on the highway at a velocity of 25 m/s. After going over a small bump in the road, the trailer detaches from the car. If the car’s speed after separation is 27 m/s and its final momentum is 35,000 kg m/s, what are the masses of the car and trailer, respectively?

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