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Conservation of Energy?

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



Two heavy balls of equal mass M are attached to the long but light metallic rod standing
on the floor. The rod with the balls falls to the floor. Find the velocity of each ball at the moment
when the rod hits the ground. Neglect mass of the rod and the friction between the balls and the
floor.


Homework Equations



E1=Ef
m1v1 + m2v2 = m1v1 + m2v2
E1 = mgh


The Attempt at a Solution



Mass 2 initial energy = mgh, mass 1(on floor) = 0
When rod falls Mass 2 = 0; mass 1 = 0.5mv^2
so mgh = 0.5mv^2

V=sqrt(2gh) ??

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
Andrew Mason
Science Advisor
Homework Helper
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Can you explain the problem better? Is there a diagram?

AM
 
  • #3
You have to take into consideration all the energies that are present in this problem. When the dumbbell is at a certain height, it has potential energy. When the Dumbbell is acceleration towards the ground, it has kinetic energy. There you have your answer. As long as you set your potential energy equal to zero at the ground just make your before and after energies equal each other, mgh = (1/2)mv^2 and just solve for v.

Edit: Hmmm, I'm looking at your question again and maybe you didn't describe it well enough. Does the dumbbell hit the floor horizontally?
 
  • #4
11
0
Yes the rod hits horizontally. Do I have to consider the normal force on the mass at the floor.

The Diagram is basically a vertical rod with one end on the floor and the other in the air. both ends have spherical masses attached to them.
 

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