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Homework Help: Determine the original velocity of the bullet

  1. May 3, 2010 #1
    Team 1 is racing out of the house to try to beat Team 2 to a site. They hop into the Convertible Porche Corvette Hybrid Jaguar that team 1 drives, and zoom away. If their position as a function of time is given by the equation x(t) = 3.81t3 + 9.882t2 + 18.6497t + 53.8946, determine the jerk, ab.cde, or how quickly the Convertible Porche Corvette Hybrid Jaguar's acceleration is accelerating. Carry it out to three places past the decimal.

    A 17 gram bullet is fired from a gun with an original velocity of vwx m/s. It collides with a 1.9 kg tupperware covered in camo duct tape, giving the tupperware a velocity of 3.68684 m/s. As the bullet approaches the second obstacle, an ammo can, it is moving 41.9412 m/s. It collides and passes through the ammo can, giving the can a velocity of .yz m/s, then the bullet drops dead as soon as it leaves the can, its velocity reduced to 0 m/s. If the ammo can has a mass of 2.3 kg and all air resistance and mass removed by collisions is neglected, determine the original velocity of the bullet and the velocity of the ammo can after the collision.


    2. see above

    3. ?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    I know nothing about physics as to solve problems. I'm trying to solve a puzzle and need the above questions solved to complete the puzzle. Any and all help is appreciated.
  2. jcsd
  3. May 3, 2010 #2


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    Homework Helper

    Y'know, this forum isn't a problem-solving service. We'll help people who are trying to do the work themselves, and if you really know nothing about physics we could make an attempt to teach you what you need to know to solve these problems (not that I necessarily expect it to work, these things are hard to learn online)... but I'm reluctant to just do it and give away an answer, and I doubt that I'm the only one here who feels that way.
  4. May 3, 2010 #3
    I'm ok with that. I would apprecitate if someone could help me understand it and how to come up with the answer myself.

    Thank you.
  5. May 3, 2010 #4


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    OK, fair enough :wink: (It's nice to see someone taking the right attitude toward learning)

    To start with: how much do you know about calculus? For instance, if I tell you that jerk is the third derivative of position with respect to time, will that get you through the first one?

    The second problem is one about conservation of momentum. Momentum is equal to mass times velocity,
    [tex]p = mv[/tex]
    (why p? who knows, but that's common usage) and when we say it's conserved, we mean that the total momentum before a collision of all objects involved in the collision is the same as the total momentum after a collision of all those same objects. So if you have two objects, A and B,
    [tex]p_{A(i)} + p_{B(i)} = p_{A(f)} + p_{B(f)}[/tex]
    where a subscript A refers to momentum of object A, subscript B refers to momentum of object B, and (i) and (f) refer to initial (before the collision) and final (after the collision) respectively. In your second problem, there are two collisions, and you can do this separately for each collision.
  6. May 3, 2010 #5
    I don't know anything about calculus... However what you wrote above isn't Greek. Yet, I don't have an idea of where to start.
  7. May 3, 2010 #6


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    More to the point, it is explicitly against https://www.physicsforums.com/showthread.php?t=5374".

    Last edited by a moderator: Apr 25, 2017
  8. May 3, 2010 #7


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    Oh yeah, that too (I had a feeling it was in the policy somewhere).
    Hmm... that could be a problem. If you have to learn what a derivative is, this isn't the place to do it.

    The second question should still be doable, as long as you can do algebra... all you need to do is set up some equations and solve them. There's no need to take the derivative of anything for that, so no calculus involved. If you want to give it a try, we can point out any mistakes.
    Last edited by a moderator: Apr 25, 2017
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