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 Posted: Wed Jun 28, 2006 7:18 am
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Posted: Wed Jun 28, 2006 8:46 am
aww I'm sorry- if you need any help, I can try to help you, though? 3nodding
And great job on finishing finals, you guys!!
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darkphoenix1247 Vice Captain
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Posted: Wed Jun 28, 2006 9:10 am
Man. My finals were easy! But that was a month ago....
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Posted: Thu Jun 29, 2006 7:36 am
I was talking to my friend after the test, and he was making fun of one of the questions because it seemed so easy.
The question was if there is a cart that weighs 0.8(kg) is going along a rail at 2(m/s), and a ball that weighs 0.4(kg) falls from an unknown hight right above the cart, and sticks to its bottom, does the cart change it's speed? If so, by how much, and if not, expain why.
He was all happy saying it didn't change speed, so he didn't know why they gave us the speeds and weight. And then I was like... dude... I hate to break it to you, but got it wrong xd .
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Posted: Thu Jun 29, 2006 9:44 am
nathan_ngl I was talking to my friend after the test, and he was making fun of one of the questions because it seemed so easy. The question was if there is a cart that weighs 0.8(kg) is going along a rail at 2(m/s), and a ball that weighs 0.4(kg) falls from an unknown hight right above the cart, and sticks to its bottom, does the cart change it's speed? If so, by how much, and if not, expain why. He was all happy saying it didn't change speed, so he didn't know why they gave us the speeds and weight. And then I was like... dude... I hate to break it to you, but got it wrong xd . i hate it when i do crap like that. i never know what i'm talking about though, so i should get used to it.
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Posted: Thu Jun 29, 2006 10:27 am
nathan_ngl I was talking to my friend after the test, and he was making fun of one of the questions because it seemed so easy. The question was if there is a cart that weighs 0.8(kg) is going along a rail at 2(m/s), and a ball that weighs 0.4(kg) falls from an unknown hight right above the cart, and sticks to its bottom, does the cart change it's speed? If so, by how much, and if not, expain why. He was all happy saying it didn't change speed, so he didn't know why they gave us the speeds and weight. And then I was like... dude... I hate to break it to you, but got it wrong xd . hmm....What is the answer? sweatdrop Haven't had a full year of physics yet-sorry; took bio and chem instead sweatdrop
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darkphoenix1247 Vice Captain
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Posted: Thu Jun 29, 2006 4:34 pm
Well, the momentum on the plain the cart was moving in (vector X) is conserved before and after the collision. Momentum, or P, is equivlant to the mass times the velocity (P=(M*V)). The rule of "conservatism of momentum" means that the sum of momentum of all objects in the system are equal before and after the colission.
Conserved momentum: P1 = P2.
Momentum: P = (M*V).
Now, since there is more than one object in the system, the momentum is equivlant to: P = (M1*V1) + (M2*V2).
And so, the conserved momentum equasion developes into:
M1*V1 + M2*V2 = M1*U1 + M2*U2
Explanation:
M1 = 0.8(kg), cart. M2 = 0.4(kg), ball.
V1 is the velocity of the cart before the collision (we know this is 2(m/s), as it was given in the question).
U1 is the velocity of the cart after the collision.
V2 is the velocity of the ball before the collision.
U2 is the velocity of the ball after the collision.
However, since the ball and the cart connected, it's okay to assume that U1 and U2 are equal, because they are then moving together, with a unified velocity, and so: U1=U2=U, meaning:
M1*V1 + M2*V2 = M1*U1 + M2*U2
M1*V1 + M2*V2 = M1*U + M2*U
M1*V1 + M2*V2 = U*(M1+M2)
Now, since we know the ball had no speed in it's X vector and that means V2=0 (note - The speed it was falling downards is in the Y vector and it doesn't interest us, since there is no momentum conservatism in vector Y, as it is crashing headlong into the cart, and the cart is held back infinately by the rails), meaning:
M1*V1 + M2*V2 = U*(M1+M2)
M1*V1 + M2*V2 = U*(M1+M2)
M1*V1 = U*(M1+M2)
And lets calculate:
M1*V1 = U*(M1+M2)
0.8*2 = U*(0.8+0.4)
1.6 = 1.2*U
1.6/1.2 = U
1.3333(m/s) = U
The final speed of the cart was: four thirds of a meter per second.
note - sorry, a few corrections and revisions were made, so re-read xd .
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Posted: Thu Jun 29, 2006 6:41 pm
Yeah...that went way over my head! YAY!
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Posted: Thu Jun 29, 2006 11:44 pm
kingpinsqeezels Yeah...that went way over my head! YAY! At what velocity? ninja rofl sorry, I had to to that xD
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Posted: Thu Jun 29, 2006 11:48 pm
nathan_ngl kingpinsqeezels Yeah...that went way over my head! YAY! At what velocity? ninja rofl sorry, I had to to that xD*cries* 3!
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Posted: Thu Jun 29, 2006 11:49 pm
kingpinsqeezels nathan_ngl kingpinsqeezels Yeah...that went way over my head! YAY! At what velocity? ninja rofl sorry, I had to to that xD*cries* 3! Yes! You win a cookie 3nodding .
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Posted: Fri Jun 30, 2006 12:03 am
nathan_ngl kingpinsqeezels nathan_ngl kingpinsqeezels Yeah...that went way over my head! YAY! At what velocity? ninja rofl sorry, I had to to that xD*cries* 3! Yes! You win a cookie 3nodding . YAY!
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Posted: Fri Jun 30, 2006 12:30 am
Okay, any questions about judaism now? xd . No more physics ninja !!!
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Posted: Fri Jun 30, 2006 12:33 am
Ooo!
I got one.
Why are we obsessed with round, doughy, chewy things with holes in the middle (meaning: The Bagel)?
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Posted: Fri Jun 30, 2006 7:19 am
Donovinhs Knight Ooo! I got one. Why are we obsessed with round, doughy, chewy things with holes in the middle (meaning: The Bagel)? mm...cause they're delicious. that's why.
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