A-level physics vector momentum help

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Iehtesam
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#1
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#1
can someone help me out with question number 2.a in this: https://imgur.com/a/NBpiR6R
the solution is this: https://i.imgur.com/fANa0KN.jpg

couldn't understand the path the cue ball is meant to take and how it can be mathematically worked out
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Eimmanuel
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(Original post by Iehtesam)
can someone help me out with question number 2.a in this: https://imgur.com/a/NBpiR6R
the solution is this: https://i.imgur.com/fANa0KN.jpg

couldn't understand the path the cue ball is meant to take and how it can be mathematically worked out
Have you studied conservation of linear momentum?
If yes, apply the conservation law to find the velocity of the cue ball.
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Iehtesam
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(Original post by Eimmanuel)
Have you studied conservation of linear momentum?
If yes, apply the conservation law to find the velocity of the cue ball.
yes, i have. i also did calculate the velocity of the cue ball from the momentum before = momentum after method. what do you do afterwards? how can i find the direction it goes as it says in the solution?
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Eimmanuel
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(Original post by Iehtesam)
yes, i have. i also did calculate the velocity of the cue ball from the momentum before = momentum after method. what do you do afterwards? how can i find the direction it goes as it says in the solution?
Velocity is a vector, so it has both magnitude and direction.
Indeed, if you have calculated the velocity, you would have the answer.
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Iehtesam
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(Original post by Eimmanuel)
Velocity is a vector, so it has both magnitude and direction.
Indeed, if you have calculated the velocity, you would have the answer.
from the solution:

"the cue balls velocity is virtually the same as the black ball"

the velocity i calculated for the cue ball is 1.76 m/s, where the velocity of the black ball is 4.24 m/s. it also says in the solution that the cue ball ends up in the bottom corner hole, and also that it's at a 45° downward trajectory, how did they find that? i basically want to know how i can mathematically confirm the cue balls trajectory into the bottom corner hole
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Eimmanuel
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(Original post by Iehtesam)
from the solution:

"the cue balls velocity is virtually the same as the black ball"

the velocity i calculated for the cue ball is 1.76 m/s, where the velocity of the black ball is 4.24 m/s. it also says in the solution that the cue ball ends up in the bottom corner hole, and also that it's at a 45° downward trajectory, how did they find that? i basically want to know how i can mathematically confirm the cue balls trajectory into the bottom corner hole
How do you find the speed of the cue ball?

It would be good that you post your working.
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Iehtesam
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(Original post by Eimmanuel)
How do you find the speed of the cue ball?

It would be good that you post your working.
with momentum before = momentum after
(.17x6) + (.17x0) = (.17xV) + (.17x4.24)
V=1.76 m/s
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Eimmanuel
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(Original post by Iehtesam)
with momentum before = momentum after
(.17x6) + (.17x0) = (.17xV) + (.17x4.24)
V=1.76 m/s
First of all, note that momentum is a vector and the 0.17*6.00 is the linear momentum of the cue ball along the x-direction.

0.17*4.24 is the linear momentum of the black ball along north-east direction.

You need to apply the conservation of linear momentum along x- and y- direction independently to find the final speed of the cue ball.

https://www.youtube.com/watch?v=4BgxSagEito
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Iehtesam
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(Original post by Eimmanuel)
First of all, note that momentum is a vector and the 0.17*6.00 is the linear momentum of the cue ball along the x-direction.

0.17*4.24 is the linear momentum of the black ball along north-east direction.

You need to apply the conservation of linear momentum along x- and y- direction independently to find the final speed of the cue ball.

https://www.youtube.com/watch?v=4BgxSagEito
couldn't thank you enough. you've saved my stupid life. i was contemplating my entire existence because of this one bloody question. finally got the bit I didn't know of quite well. thank you
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