Not only energy but also momentum. Taken together it follows: If a moving mass elastically hits an identical resting mass, it transfers all momentum to it.techmologist said:I know energy is roughly conserved.
Not sure if the gaps are needed. Video of a large scale model, here you can see that the ball does bounce back a bit, and that it's not perfect, with gaps bewteen some balls and not the others.techmologist said:I'm wondering if there are small gaps between the five balls or if they are touching when they hang at rest.
techmologist said:In the picture there are five balls. If you pull one back and let it smash into the other four, it transfers all its momentum and energy, and the ball on the other end pops off with that same momentum. But this would not happen if we replaced the four identical balls with one ball which has four times the mass. The first ball would bounce back off the heavy ball without transferring all its energy.
It makes no difference whether the balls are touching or not. As long as each ball is able to freely rebound off the other balls, the action will be observed.techmologist said:I'm wondering if there are small gaps between the five balls or if they are touching when they hang at rest.
techmologist said:I know this satisfies the conditions of conservation of momentum and energy, but it doesn't seem like the only possible result that could satisfy those conditions. So how is the momentum and energy communicated from one end to the other?
You can see it as happening successively. The inner of the two pulled balls, kicks off the most outer ball on the other side. Then the outer pulled ball impacts and kicks of the second ball on the other side.techmologist said:But what about when you pull back two balls and release them? ...(whether or not it is transferred to each one successively, I don't know).
TurtleMeister said:It makes no difference whether the balls are touching or not. As long as each ball is able to freely rebound off the other balls, the action will be observed.
Here's another link that addresses that question.
http://www.lhup.edu/~dsimanek/scenario/cradle.htm
Jeff Reid said:Not sure if the gaps are needed. Video of a large scale model, here you can see that the ball does bounce back a bit, and that it's not perfect, with gaps bewteen some balls and not the others.
http://www.youtube.com/watch?v=mFNe_pFZrsA&fmt=18
The Newton's Cradle works by demonstrating the law of conservation of energy and momentum. When one ball on the end is lifted and released, it transfers its energy to the next ball, causing it to swing out and then back. This continues until the energy is transferred to the last ball and the first ball comes back to hit it, starting the process over again.
A Newton's Cradle is often used as a desk toy for entertainment, but it also serves as a demonstration of physics principles such as energy conservation and transfer of momentum.
A Newton's Cradle typically has 5 or 7 balls, although there are versions with more or less. The number of balls does not affect the physics principles demonstrated.
Although it is not typically used as a scientific tool, a Newton's Cradle can be used to demonstrate the laws of energy and momentum, making it a useful teaching aid in physics classrooms.
No, a Newton's Cradle is not a perpetual motion machine. The energy and momentum eventually dissipate due to friction and air resistance, causing the balls to eventually come to a stop.