# Newtons cradle velocity

if you have a newton's cradle consisting of, say, 5 balls, and you displace 2 of these to the left and let them go, we say they hit the others with velocity v. I was just wondering if the balls would have different velocities at the point of impact since they will have inevitably fallen from slightly different heights (i.e more GPE = more KE?) Does the back one speed up more and then just push the second one so they do have the same velocity? thanks.

## Answers and Replies

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krab
since they will have inevitably fallen from slightly different heights (i.e more GPE = more KE?) .
I don't know why you say that. Each ball is suspended from its own identical string. Pull 2 aside by some distance, they both rise the same distance.

Andrew Mason
Homework Helper
if you have a newton's cradle consisting of, say, 5 balls, and you displace 2 of these to the left and let them go, we say they hit the others with velocity v. I was just wondering if the balls would have different velocities at the point of impact since they will have inevitably fallen from slightly different heights (i.e more GPE = more KE?) Does the back one speed up more and then just push the second one so they do have the same velocity? thanks.
The most outward ball has the highest amplitude so it should have the greatest horizontal speed at the bottom. But it can't go any faster that the one in front of it, so it pushes it forward and they both move at the same speed.

Edit: On second thought, I think Krab is right. They both have the same amplitude so they both move at the same speed. They are suspended from their own strings so each ball is an identical pendulum.

AM

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yeah thanks, just been messing around with one i found and your right!