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Meteorite falling on a Car...

  1. 1. The problem statement, all variables and given/known data

    A 27 pound meteorite fell and struck a car, creating a dent about 28 cm deep. If the initial speed of the meteorite was 530 m/s, what was the magnitude of the average force exerted on the meteorite by the car?

    2. Relevant equations

    Vf^2=Vi^2+2ad
    F=ma

    3. The attempt at a solution

    Just need someone to tell me if my work is right.

    I found the acceleration using Vf^2=Vi^2+2ad it came out to be-501,607 m/s^2

    I to the mass of the meteorite 27/2.2= 12.273 kg and multiplied it my the acceleration and came up with 6.156 MN.

    Did I do this problem right?
     
  2. jcsd
  3. PhanthomJay

    PhanthomJay 6,242
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    Not quite. Using F =ma gives you the net average force acting on the meteorite. Threre is more than one force acting. You are asked to find the force of the car on the meteorite.
     

  4. Isn't the force equal but opposite?
     
  5. nrqed

    nrqed 3,048
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    Your calculation seems right to me (I did not check the numbers, just the method)

    Patrick
     
  6. AlephZero

    AlephZero 7,300
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    I suppose PhantomJay is referring to other forces on the meteorite such as its own weight.

    Its weight of 12.273*9.8 N = 0.00012 MN is negligible compared to the force caused by the impact, so it is reasonable to ignore it.

    The question doesn't say what direction the meteorite was travelling, and if you have ever seen a "shooting star", there is no reason to assume it would be falling vertically downwards. So even if you did want to include the weight, you don't know how to add the two force vectors.
     
  7. PhanthomJay

    PhanthomJay 6,242
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    Yes, I was referring to the weight, however, you are correct, it is negligible and the direction is unknown anyway. I should have looked at the numbers first.
     
  8. AlephZero

    AlephZero 7,300
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    So should the person who invented the question, IMO. A 27 lb meteorite travelling at 530 m/sec wouldn't make a 28 cm deep dent in the car, it would make a hole in the roof and another hole in the floor.

    (I've worked on what happens when parts of jet engines break, and I know how much damage a 20 lb object travelling at "only" 200 m/sec can do, because I've seen the results of the experiment).
     
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