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Easy momentum question

  • Thread starter ckaiser813
  • Start date
  • #1
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Homework Statement


A 30.00 kg mass falls from a height of 4.00m. The momentum of the mass just before it hits the ground is?


Homework Equations



obviously p=mv

The Attempt at a Solution



I just can't figure out how to get a velocity for this formula?
 

Answers and Replies

  • #2
LowlyPion
Homework Helper
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  • #3
Matterwave
Science Advisor
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There are 2 ways to do this.

1) Find the velocity using kinematic equations:
[tex]x = \frac{1}{2}gt^2[/tex]
you know x and g so you can solve for t. After solving for t you can get the velocity from [tex]v=gt[/tex].

2) You can also use energy conservation
[tex]KE=\frac{1}{2}mv^2=PE=mgh[/tex]
and then applying the knowledge of what KE is and momentum is
[tex]KE=\frac{p^2}{2m}[/tex]
to find p directly.
 
  • #4
14
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yes sir that helped me figure out what the book got, thanks a bunch!
 

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