Study Guide Physics Chapter 7, 8

  1. What is Newton’s Third Law? How often is it true?
  2. When objects collide or interact how many forces are there? Is this always true?
  3. When objects collide how does the force on object one compare to the force on object two?
  4. When objects collide how does the acceleration on object one compare to the acceleration on object two if the masses of the two objects are different?
  5. Be able to state Newton’s Third Law for various situations:

a)Bat and Ball

b)Apple and Earth

c)Hand and Board (karate)

  1. Why can a horse pull a cart when Newton’s Third says that the force on the cart and the force on the horse are equal and opposite?
  2. Why can a rocket propel itself in space when there is no air to push against?
  3. What two factors does momentum depend on?
  4. Which has more momentum a small bus or a large bus when both are moving at the same speed?
  5. Which has more momentum a bus moving slowly or the same bus moving fast?
  6. What is an Impulse?
  7. Why do cars have padded dash boards, seatbelts, and air bags?
  8. How does the force, acceleration, impulse, and change in velocity compare when a bat hits a baseball?
  9. What happens to Joey if he pushes a bowling ball away from him while he is on slippery ice? How is the motion of the two different and why?
  10. If one car collides with and sticks to another car that has the same mass, how fast will the two cars move in comparison to the first car?
  11. What causes a greater impulse, sticking or bouncing and why?

Practice Problems

  1. A 50 kg swimmer pushes off the wall with a force of 100 N. What is the acceleration of the swimmer?
  2. A 0.2 kg bullet traveling a 100 m/s hits the safety wall (made of sand) behind the targets at a shooting range and comes to a stop in 0.5 seconds. What is the average force on the bullet?
  3. One train car of mass 1000 kg moving at a velocity of 5 m/s couples with a second train car of mass 300 kg that is stationary. What is the velocity of the two cars that are now stuck together?
  4. A 70 kg astronaut and his alien girlfriend have a fight and push away from each other while floating in space. If the alien is 50 kg and moves away at a velocity of 10 m/s, what will be the velocity of the astronaut in the other direction?
  5. What is the momentum of a 400 N student running at a velocity of 6 m/s?