momentum and 3rd law

Card Set Information

momentum and 3rd law
2010-02-01 17:40:45

midterm 3
Show Answers:

  1. define impulse
    What is the force felt by an object in a specific time period or I=Ft?
  2. The momentum of an object depends on
    What is the object’s mass and its velocity
  3. How does the impulse applied to an object affect the object’s momentum -
    What is Ft = Dmv or the impulse applied induces a change in the object’s momentum?
  4. In collisions or explosions in an isolated system the law that applies is
    What is the Conservation of Momentum
  5. As a tennis ball bounces off a wall, how is its momentum affected?
    What is its momentum is reversed and slightly decreases
  6. An insect flying through the air smacks into the windshield of a rapidly-moving train. Is the force the windshield exerts on the insect higher than the force the insect exerts on the windshield.
    What is false? The force the windshield exerts on the insect is the same as the force the insect exerts on the windshield.
  7. Friction provides the force which "pushes" a car forward as it accelerates down the road. (Assume a flat road.)
    What is True ? To accelerate an object requires an external force.
  8. Susan throws a ball in the air. After the ball leaves her hand, the ball accelerates in the upward direction as it is moving upward and accelerates in the downward direction as it is moving downward.
    What is False? After the ball leaves Susan's hand, the acceleration is always downward even when the ball is moving upward.
  9. If a car hits a tree, the car’s occupants (assume no seat belts or air bags) will be violently thrown forward due to a force created by the car seats.
    What is False ? There is no force throwing the person forward.
  10. Ben travels to a distant planet. In outer space, with essentially no gravity, he can throw a baseball (mass = 0.5 kg) and a shot put (mass = 4 kg) at the same speed with no discernable difference in effort.
    What is False? According to Newton’s second law, force equals mass times acceleration. If the objects are thrown at the same speed by the same person they must have the same acceleration. For the same acceleration the force exerted by the person’s arm has to be much higher for the more massive object. Gravity, or the lack of it, does not change the fact that the shot put will always be harder to throw. It has more inertia.