physics anyone? - UBB.Developers

UBB.Dev

I need some homework help. It's a level 3 problem; hardest. I've stared at this for what seems like forever and haven't the slightest idea how to do it without them giving me some more info. But the book says it can be solved and the answers in the back of the book are below.

Problem #27:
A 0.280kg croquet ball makes an elastic head-on collision with a second ball initially at rest. The second ball moves off with half the original speed of the first ball. (a) What is the mass of the second bal? (b) What fraction of the original kinetic energy (ΔKE/KE) gets transferred to the second ball?

Answers:
(a) 0.840kg
(b) 0.750

[ 01-13-2002 10:26 AM: Message edited by: DPK ]

Are those answers the possible choices, or are they answers that you came up with?

quote:
Originally posted by DPK:
the book says it can be solved and the answers in the back of the book are below.

I'm guessing those are the answers from the back of the book.

D'oh! Of course.

Nevermind

[ 01-13-2002 12:11 AM: Message edited by: Jamin ]

While I think about how to go about solving this problem, the symbol to make an uppercase delta is "Δ" which equals Δ.

[ 01-13-2002 12:19 AM: Message edited by: Matt Jacob ]

thanks matt, updated my post.

*scratches head*
yes...
....of course I knew that...*cough*

I believe you'll need to draw a vector diagram for this, and then split the vectors. I'll do some research today and try to formulate an answer.

If you apply conservation of momentum (mv) and conservation of energy (1/2mv^2) to the system, you get two equations, but there are three unknowns: mass of second ball, initial speed of first ball and final speed of first ball.

It's been a while since I've studied physics, but it does seem like you need more information. I could be wrong.

I think I'm going to have to agree about not having enough information available. We need some unit of speed in order to solve the problem.

Check out this page for a similar problem and a step-by-step solution.

I hate prentice hall and their stupid examples with poor explanations that have nothing to do with the actual problems at the end of the chapter.

It'd be so easy to solve this if velocity was supplied. :

Thankyou matt and dave for your help pointing me in the right direction.

[ 01-13-2002 06:19 PM: Message edited by: DPK ]

DPK, you don't need the exact velocity. Put one as X and the other as 0.5X in the equation. That X will be eliminated after some calculating

aleina