Pages: 1

 

2008-10-27 18:36:35
aj0404
It'll just be our little secret
+298|6799|Iowa...
alright so basically i missed all of last week with bronchitis and i have no idea what's going on with this class. apparently we're doing momentum, which seems very simple but i guess i'm missing something (probably because the teacher doesn't do his job). our homework is given online, and you're given 5 chances to get the correct answer. i've tried 4 times.
here's the problem:

https://img183.imageshack.us/img183/1933/helprm1.jpg

i've tried a bunch of different ways to get this but apparently they're all wrong. help would be greatly appreciated, along with explanation of how to do the problems. obviously karmaz will be awarded.
2008-10-27 19:03:49
san4
The Mas
+311|7138|NYC, a place to live
I flunked out of college physics on a version of that problem.

Good luck.


Edit: have you seen this link? http://en.wikipedia.org/wiki/Momentum#H … nsional.29

Last edited by san4 (2008-10-27 19:12:41)

2008-10-27 19:07:57
AussieReaper
( ͡° ͜ʖ ͡°)
+5,761|6603|what

Can you tell us what your previous answers were so we don't give you the same result?

(I dropped physics in highschool)
https://i.imgur.com/maVpUMN.png
2008-10-27 19:12:08
Flaming_Maniac
prince of insufficient light
+2,490|7157|67.222.138.85
v1m1 + v2m2 = v1m1 + v2m2

107.3kg(5m/s) + 85.7kg(4.9m/s) = 107.3kg(4.1m/s) + 85.7kg(x)

solve for x, and note that all the velocities are in the same direction

edit: shit my bad I was looking at the last question, not the one you've been missing.
2008-10-27 19:22:27
aj0404
It'll just be our little secret
+298|6799|Iowa...

Flaming_Maniac wrote:

v1m1 + v2m2 = v1m1 + v2m2

107.3kg(5m/s) + 85.7kg(4.9m/s) = 107.3kg(4.1m/s) + 85.7kg(x)

solve for x, and note that all the velocities are in the same direction
ah,so it's simply a conservation of momentum thing. tbh i didn't even see the 4.10 m/s thing (not that i would've known what to do with it anyway).

so then the velocity of the player would be 6.03 m/s and the momentum would be 517 kgm/s?
2008-10-27 19:25:03
Flaming_Maniac
prince of insufficient light
+2,490|7157|67.222.138.85

aj0404 wrote:

Flaming_Maniac wrote:

v1m1 + v2m2 = v1m1 + v2m2

107.3kg(5m/s) + 85.7kg(4.9m/s) = 107.3kg(4.1m/s) + 85.7kg(x)

solve for x, and note that all the velocities are in the same direction
ah,so it's simply a conservation of momentum thing. tbh i didn't even see the 4.10 m/s thing (not that i would've known what to do with it anyway).

so then the velocity of the player would be 6.03 m/s and the momentum would be 517 kgm/s?
Yeah you got it, ignore my edit. They kinda asked the questions in a backward fashion. Assuming you plugged in correctly to find the final velocity of the second hockey player and then multiplied that by his mass to find his final momentum, you did it right.
2008-10-27 20:18:22
theit57
I am THE Frodo Baggins.
+124|6849|6 feet under

Flaming_Maniac wrote:

v1m1 + v2m2 = v1m1 + v2m2

107.3kg(5m/s) + 85.7kg(4.9m/s) = 107.3kg(4.1m/s) + 85.7kg(x)

solve for x, and note that all the velocities are in the same direction

edit: shit my bad I was looking at the last question, not the one you've been missing.
correction:

M1V1+M2V2=(M1+M2)V'
2008-10-27 20:48:20
aj0404
It'll just be our little secret
+298|6799|Iowa...
okay new problem...

https://img185.imageshack.us/img185/4313/helpagainla6.jpg

at first i thought you would just add the masses and multiply but i guess not. i'm guessing it has something to do with adding the two momentums together because they're in opposite directions. only problem is, it keeps telling me the answer i get for the pellets is wrong, and i think i need that to find the system...
2008-10-27 21:03:23
VicktorVauhn
Member
+319|6842|Southern California
with no external forces the sum of the the momentum before is the sum of the momentum after, they started with 0, so the sum after must be 0... in other words its the same number just positive.

from there just use momentum = mv and the given mass of the pellets to find the velocity...

also read the damn book
These are all the same question

Last edited by VicktorVauhn (2008-10-27 21:03:58)

2008-10-28 00:40:39
RandomSchl
|\/|€|\/|߀|2
+52|6893|California
My physics teacher uses WebAssign for my class also.

Last edited by RandomSchl (2008-10-28 00:40:59)

2008-10-28 00:44:30
VicktorVauhn
Member
+319|6842|Southern California

RandomSchl wrote:

My physics teacher uses WebAssign for my class also.
I am all done with physics
*break dances a little*

(then remembers that the rest of my classes are basically like harder versions of physics...)
2008-10-28 05:38:10
Flaming_Maniac
prince of insufficient light
+2,490|7157|67.222.138.85

theit57 wrote:

Flaming_Maniac wrote:

v1m1 + v2m2 = v1m1 + v2m2

107.3kg(5m/s) + 85.7kg(4.9m/s) = 107.3kg(4.1m/s) + 85.7kg(x)

solve for x, and note that all the velocities are in the same direction

edit: shit my bad I was looking at the last question, not the one you've been missing.
correction:

M1V1+M2V2=(M1+M2)V'
incorrect

That is the equation for inelastic collisions only, of which the original problem is not.

 

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