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Homework Help: Explosion question

  1. May 30, 2005 #1
    Hey everyone! I'm a newbie here, how are you all today?
    Anywho, I was doing my physics homework and I came across this question, and I'm stuck :( Can anyone tell me just how to start it?

    A shell is shot with an initial velocity of 20 m/s, at an angle of 60 degrees with the horizontal. At the top of the trajectory, the shell explodes into two fragments of equal mass. One fragment, whose speed immediately after the explosion is zero, falls vertically. How far from the gun does the other fragment land, assuming that the terrain is level and that air drag is negligible?

    Totally stuck! Don't even know where to start :(
    Thanks for your help!
  2. jcsd
  3. May 30, 2005 #2
    edit: scratch my idea. I have to think about this more.

    2nd edit: ok. Assuming the the explosion means "breaks into two parts without making too much of a fuss" and air resistance is neglected the system's momentum's x-component is conserved and you can solve the x component of velocity of the half that keeps moving in the x-direction. Can you do it from here on?

    If approached like this the problem is so unrealistic that I'm not sure if I'm giving you good advice. Maybe some of the official homework helpers could confirm this? It feels odd to think about a system that breaks up like this but since you can break up the equations of motions into components the system's momentum's x-component should be conserved.
    Last edited: May 30, 2005
  4. May 30, 2005 #3


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    I will assume you can find the position of the shell at explosion. At that time the velocity is horizontal. Momentum will be conserved. Immediately after explosion one half of the shell will be at rest, then it falls. How fast and in what direction will the other half be moving immediately after the explosion? How does the horizontal distance travelled after explosion compare to the horizontal distance travelled before the explosion?
  5. May 30, 2005 #4
    wahh! I doubted myself in vain.
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