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P2: Momentum and kinetic energy question help!

Hi...I was just wondering if anybody could help explain this question to me:

Two trolleys, of mass 2kg and 5kg, are at rest and in contact on a smooth, level surface. A coiled spring in one trolley is released so that they 'explode' apart. The lighter trolley moves off at 50cm/s.

a. Find the speed of the heavier trolley
b. Find the minimum energy which was stored in the coiled spring before release.

At the moment, I THINK I've found the velocity of the heavier trolley, but I don't understand how to answer the second part of the question. I've attached a scan of what I've tried to do, but really not too sure :/

Thanks in advance!

EDIT: Just realised they are looking for speed in part A, so it'd be +0.2m/s not -0/2 m/s...

(edited 12 years ago)

Total kinetic energy of the trolleys afterwards has to at least equal the minimum energy stored in the coiled spring before.

Reply 2

Nistar

9

Original post by CheeseLord

Hi...I was just wondering if anybody could help explain this question to me:

Two trolleys, of mass 2kg and 5kg, are at rest and in contact on a smooth, level surface. A coiled spring in one trolley is released so that they 'explode' apart. The lighter trolley moves off at 50cm/s.

a. Find the speed of the heavier trolley
b. Find the minimum energy which was stored in the coiled spring before release.

At the moment, I THINK I've found the velocity of the heavier trolley, but I don't understand how to answer the second part of the question. I've attached a scan of what I've tried to do, but really not too sure :/

Thanks in advance!

EDIT: Just realised they are looking for speed in part A, so it'd be +0.2m/s not -0/2 m/s...

I think what you've done is correct. Just so I can check, is this in the AQA text book? :biggrin:

Reply 3

CheeseLord

OP

6

I didn't get it from the textbook, was just googling for some trickier momentum questions for revision, and it came up with a list of Qs! Thanks for helping confirm though...are you doing the exam tomorrow as well?? :biggrin:

Reply 4

Nistar

9

Original post by CheeseLord

I didn't get it from the textbook, was just googling for some trickier momentum questions for revision, and it came up with a list of Qs! Thanks for helping confirm though...are you doing the exam tomorrow as well?? :biggrin:

Indeed I am. Revising as we speak and will attempt some more papers in a while. How you feeling? :smile:

Reply 5

CheeseLord

OP

6

Original post by Nistar

Indeed I am. Revising as we speak and will attempt some more papers in a while. How you feeling? :smile:

About to get a early night...don't feel completely ready, but am probably going to read through the guide once more tomorrow and hopefully I should be fine :rolleyes:

Good luck for tomorrow!!

Reply 6

x.parisha.x

2

Original post by MotsMan

Total kinetic energy of the trolleys afterwards has to at least equal the minimum energy stored in the coiled spring before.

How do you work out the kinetic energy beofre ?

Original post by x.parisha.x

How do you work out the kinetic energy beofre ?

Welcome to TSR, I understand that you are new to TSR.
Please do not post in an old thread like this. If you need help on such an old thread, start a new thread and link to the old thread.

As for your question, there is no KE before the "explosion".
If you still need help, start a new thread as the thread will be closed soon.

P2: Momentum and kinetic energy question help!

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