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Homework Help: Help w/Physics ?

  1. Aug 28, 2003 #1
    The question says that a hunter aims directly at a target (on the same level) 120 m away. If the bullet leaves the gun at a speed of 250m/s, by how much will it miss the target?

    So my values are v_o=250m/s, r=120m, and angle=0 since they're on the same level, right? And I need to know v to subtract from 120m.

    I would just like to know what equation to use, not the answer to the problem. Thank you.
  2. jcsd
  3. Aug 28, 2003 #2


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    Science Advisor

    The acceleration downward is 9.8 m/s2 so dv/dt= -9.8.
    Integrating (or, since this is a constant, just mutiplying)
    v= -9.8t+ initial vertical velocity= -9.8t+ 0 so v= dy/dt= -9.8t.
    Integrating that, y= -4.9t2+ initial height= -4.9t2.

    Neglecting air resistance (which we have to since there is no information on air resistance) there is no horizontal acceleration:
    a= dv/dt= 0 so v= initial horizontal velocity= 250 m/s. and then
    x= 250t. To go 120 m, requires that 250t= 120. Solve that equation for t and use that t in y= -4.9t2 to find how much the bullet has dropped.
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