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1 dimentional kinematics problem. please help! due in 5 hours

  1. Jan 19, 2010 #1
    1. The problem statement, all variables and given/known data
    A bolt comes loose from underneath an elevator that is moving upward at a speed of 7.1 m/s. The bolt reaches the bottom of the elevator shaft in 3.6 s.
    (a) How high up was the elevator when the bolt came loose?

    (b) What is the speed of the bolt when it hits the bottom of the shaft?

    2. Relevant equations
    v=v0+ at
    V^2=V0^2 -2a(x-x0)

    3. The attempt at a solution

    Im confused as if the acceleration of the elevator is constant or not, i cant seem to find it
  2. jcsd
  3. Jan 19, 2010 #2
    The elevator is not accelerating, it only has a velocity.
    You can find the height of the elevator using the equation for velocity: v=x/t.
    You are trying to find x; you have t and v.
    What do you have to do to find x?

    To find the speed of the bolt when it hits the ground, remember that a=v/t. You are trying to find v (the speed), and you have t. You also have a, which is the acceleration due to gravity, 9.8 m/s2. You just need to do simple algebra for both of these problems.

    Oh, by the way, remember that if something just has a velocity, its acceleration is zero. The equations you have listed are more complicated than this problem requires, but when you need them later, something moving with constant velocity has zero acceleration. So you might just need the x0 + v0t parts of the equation, for example.
    Last edited: Jan 19, 2010
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