#80365
01/12/2002 11:29 PM
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Joined: Nov 2000
Posts: 915
Developer
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Developer
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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 ]
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#80366
01/13/2002 12:41 AM
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Joined: Sep 2000
Posts: 4,211
Master Hacker
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Master Hacker
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Are those answers the possible choices, or are they answers that you came up with?
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#80367
01/13/2002 12:58 AM
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Joined: Sep 2000
Posts: 793
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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.
-DT
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#80368
01/13/2002 1:00 AM
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Joined: Sep 2000
Posts: 4,211
Master Hacker
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Master Hacker
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D'oh! Of course.
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#80369
01/13/2002 1:10 AM
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Joined: Mar 2000
Posts: 3,594
Moderator / Template Diva
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Moderator / Template Diva
Joined: Mar 2000
Posts: 3,594 |
Nevermind
[ 01-13-2002 12:11 AM: Message edited by: Jamin ]
Don't put that signature in your mouth! You don't know where it's been!
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#80370
01/13/2002 1:18 AM
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Joined: Sep 2000
Posts: 4,211
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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 ]
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#80371
01/13/2002 11:26 AM
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Joined: Nov 2000
Posts: 915
Developer
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Developer
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thanks matt, updated my post.
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#80372
01/13/2002 1:34 PM
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Joined: Jan 1999
Posts: 568
Moderator / Fish
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Moderator / Fish
Joined: Jan 1999
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*scratches head* yes... ....of course I knew that...*cough*
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#80373
01/13/2002 2:35 PM
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Joined: Sep 2000
Posts: 4,211
Master Hacker
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Master Hacker
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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.
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#80374
01/13/2002 3:12 PM
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Joined: Aug 2000
Posts: 335
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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.
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#80375
01/13/2002 4:01 PM
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Joined: Sep 2000
Posts: 4,211
Master Hacker
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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.
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#80376
01/13/2002 7:18 PM
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Joined: Nov 2000
Posts: 915
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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 ]
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#80377
01/13/2002 8:09 PM
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Joined: Oct 2000
Posts: 73
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Member
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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
aleina
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