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Homework Help: 2d kinematic problem

  1. Sep 3, 2014 #1
    1. The problem statement, all variables and given/known data
    A large very powerful gun shoots a bullet that easily goes through a block. In the process the block is knocked off the post and falls to the ground. Which hits the ground first, the bullet or the block. Why?

    2. Relevant equations

    3. The attempt at a solution
    I am thinking that the block would fall to the ground faster because it has a zero x component of velocity, but i'm not sure if this is true.
  2. jcsd
  3. Sep 3, 2014 #2


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    Gold Member

    Let me give you a new problem that might help you see this problem in new light.

    2 blocks are floating in space at lets say x= 0m y= 5m (they are separated on the z axis, but they won't change their z coordinates so we can ignore them, but they're not at the same point in space is what I'm getting at). We will use standard 2d coordinates, x is left and right, y is up and down. At some time I hit both blocks and they instantaneously acquire their (constant) velocities. Let's say block A moves with a velocity <5, -1> and block B moves with a velocity <0, -1> which one hits the ground first?

    Now, same initial situation, but this time they're going to accelerate. When I hit the blocks block A moves at
    <10 , -9.8t> and block B moves at <10 , -10t>. Now which one hit's the ground first?
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