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Homework Help: Multiple choice questions on work and impulse.

  1. Dec 6, 2009 #1
    On a level practice range, a 46 g golf ball is struck by a golf club and leaves teh ground witha speed of 72 m/s at an angle 40 degrees above the horizontal. how much work was done by the golf club on the golf ball?

    a. 32 J
    b. 120 J
    c. 230 J
    d. 520 J
    e. 3300 J

    It's just 1/2mv^2 right? So 120 J?

    What is the total speed of the golf ball at the highest point of its trajectory? Ignore air resistance.
    a. 0 m/s
    b. 36 m/s
    c. 46 m/s
    d. 55 m/s
    e. 72 m/s

    Its just the same as it started with right? 72 m/s?

    A piece of clay and a ball of the same mass are thrown at a wall with the same velocity. The clay sticks to the wall and the ball bounces off. Which one of the following statements is correct regarding the impulse each experiences?

    a. The clay has a larger impulse than the ball because it sticks to the wall.
    b. The ball has a larger impulse than the clay because it bounces off the wall.
    c. They have the same impulse because they have the same mass and initial velocity.
    d. No comparison can be made without knowing the amount of time the ball is in contact with the wall.

    I think the answer is b. Using mv/t, no matter what the ball is going to have less time in contact with the wall right? Or how would you even do that equation if it sticks? Is it the time it takes to come to a stop? Would it be d then?
  2. jcsd
  3. Dec 6, 2009 #2
    1b: No. The initial velocity as it left the club was partly vertical and partly horizontal. At the high point what is true of Vy? Hint: Find Vx as that is constant throughout the flight.

    2 is well reasoned.
  4. Dec 6, 2009 #3


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    Homework Helper

    The speed at the top of the trajectory is not 72. It slows down as it goes up. You'll have to separate the motion into its horizontal and vertical parts to deal with it.

    Your answers for the first and last questions are correct.
  5. Dec 6, 2009 #4
    So 55 for #2. What is the answer to the impulse question? b?
  6. Dec 6, 2009 #5
    yes, it is (b) we told you twice already!! :wink:
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