With a Newton's Cradle, apply the momentum formula to the outcome of actions if 1,2, 3, or 4 out of 5 are put into motion. Choose the mass and the velocity shall initially be 5 m/s in all examples.

Question

shane_b · Answer

See this post of the same question: http://openstudy.com/updates/50172e4ae4b04dfc808b63c4

anonymous · Answer

I saw the answer to that question but I didn't understand it and could you please explain?

shane_b · Answer

Sure.  Let's assume a mass of 0.05kg for each ball.

If one ball is in motion, the momentum will be:$$p=mv=(0.05kg)(5m/s)=0.25kgm/s$$If two balls are in motion,, the momentum will be:$$p=mv=(0.05kg+0.05kg)(5m/s)=0.50kgm/s$$etc...

anonymous · Answer

Is that all you have to do?? that almost seems too easy. Is that what the momentum is after the collision or before?

shane_b · Answer

The momentum before and after will be the same (Conservation of Momentum)...which is why if you drop 2 balls on one side, two balls on the other side move outward at the same speed (assuming they all have equal masses). 

There are some losses over time (heat, drag, etc)...but for a physics problem you can essentially ignore them unless you've been specifically instructed to consider them...which makes the problem significantly harder.

anonymous · Answer

thank you so much that helped. i just didn't understand at all..

shane_b · Answer

you're welcome :)