# Mechanics

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I proved for one case in which there will be no further collisions.But isn’t there another case in which B and C move in the same direction in which B will be at a lower speed therefore no colliding.

Last edited by Student 999; 1 month ago

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#3

B must be moving at a lower velocity than C after the collision.

Otherwise you'd have to invent the physics for B to pass through C.

Otherwise you'd have to invent the physics for B to pass through C.

Last edited by mqb2766; 1 month ago

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(Original post by

B must be moving at a lower velocity than C after the collision.

Otherwise you'd have to invent the physics for B to pass through C.

**mqb2766**)B must be moving at a lower velocity than C after the collision.

Otherwise you'd have to invent the physics for B to pass through C.

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#5

(Original post by

I know that,but I don’t know how to find the answer, is the value of k that I stated above also part of the range of values that I could be since it means that B will be stationary thus no further collisions

**Student 999**)I know that,but I don’t know how to find the answer, is the value of k that I stated above also part of the range of values that I could be since it means that B will be stationary thus no further collisions

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(Original post by

If B has negative velocity it will collide with A, so that is one limit (B post impact velocity = 0). This will occur if k is large and and effectively B bounces off a wall (heavy C). If k is small (light C), both B and C will move in the same direction after the collision and the velocity of C will be larger than B, so I can't see a lower limit for k, apart form the obvious physcial k>0.

**mqb2766**)If B has negative velocity it will collide with A, so that is one limit (B post impact velocity = 0). This will occur if k is large and and effectively B bounces off a wall (heavy C). If k is small (light C), both B and C will move in the same direction after the collision and the velocity of C will be larger than B, so I can't see a lower limit for k, apart form the obvious physcial k>0.

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#7

(Original post by

So essentially k=8 as I proved and bigger than 0.This doesn’t answer the question in the range of values k must be.

**Student 999**)So essentially k=8 as I proved and bigger than 0.This doesn’t answer the question in the range of values k must be.

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(Original post by

Ive not checked your working, but you want the post impact velocity of B to be >= 0, assuming the pre impact velocity of B is postive. That gives you a range for k, as described in the previous response

**mqb2766**)Ive not checked your working, but you want the post impact velocity of B to be >= 0, assuming the pre impact velocity of B is postive. That gives you a range for k, as described in the previous response

velocity B<=velocity A ,after impact since they could coalesce

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#9

(Original post by

It would make sense to find the lower limit of k by using inequalities whereby

velocity B<=velocity A ,after impact since they could coalesce

**Student 999**)It would make sense to find the lower limit of k by using inequalities whereby

velocity B<=velocity A ,after impact since they could coalesce

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(Original post by

I guess you need to understand (analyze the impact equation) why this is impossible, but the original reply is still valid.

**mqb2766**)I guess you need to understand (analyze the impact equation) why this is impossible, but the original reply is still valid.

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#11

(Original post by

I’m so confused.What is the answer to the it??

**Student 999**)I’m so confused.What is the answer to the it??

If you keep asking about a lower limit for k, you should do a thought experiment and understand why this won't occur.

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(Original post by

I don't know what your current answer is. You need to use the inequality in the velocity of B to get the inequality (upper limit) for k.

If you keep asking about a lower limit for k, you should do a thought experiment and understand why this won't occur.

**mqb2766**)I don't know what your current answer is. You need to use the inequality in the velocity of B to get the inequality (upper limit) for k.

If you keep asking about a lower limit for k, you should do a thought experiment and understand why this won't occur.

However I tried doing an inequality but it came out to be messy

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#13

(Original post by

My current answer is k=8

However I tried doing an inequality but it came out to be messy

**Student 999**)My current answer is k=8

However I tried doing an inequality but it came out to be messy

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(Original post by

Maybe try and make it less messy? If you're confident that k=8 corresponds to zero B velocity, it would be easy enough to argue that that would be the inequality boundary.

**mqb2766**)Maybe try and make it less messy? If you're confident that k=8 corresponds to zero B velocity, it would be easy enough to argue that that would be the inequality boundary.

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#15

(Original post by

Could Veocity of C be the same as velocity of B

**Student 999**)Could Veocity of C be the same as velocity of B

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(Original post by

Doing thought experiments like these can be useful, but you should put the scenarios into the equation(s) and see what comes out.

**mqb2766**)Doing thought experiments like these can be useful, but you should put the scenarios into the equation(s) and see what comes out.

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**mqb2766**)

Doing thought experiments like these can be useful, but you should put the scenarios into the equation(s) and see what comes out.

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#18

(Original post by

You can’t put this into equations since I’m setting the boundaries of the values of what k could be therefore I’ll have to decide if it’s possible

**Student 999**)You can’t put this into equations since I’m setting the boundaries of the values of what k could be therefore I’ll have to decide if it’s possible

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#19

(Original post by

**Student 999**)
Last edited by mqb2766; 1 month ago

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(Original post by

Can you post the full working, so the bits before you write v1 (and what does it refer to etc).

**mqb2766**)Can you post the full working, so the bits before you write v1 (and what does it refer to etc).

V2 refers to velocity of C

Last edited by Student 999; 1 month ago

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