M1 hard moment question help please;(

hi I am stuck on part b as I don't understand where I have gone wrong.

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I have worked out what T would be and equate it with TQ found in part a but it doesn't work. Why is that. Also for part c, it is asking you to prove that x is less than 2 right ? For this I don't get why w can be equal to 0. How do you know when w can be 0 or not ?? Thanks so much . Also how do I answer c I am kind of lost.

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Reply 1

Notnek

Original post by coconut64

hi I am stuck on part b as I don't understand where I have gone wrong.

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For b) I agree with your answer but you can make it a bit nicer by multiplying top and bottom by 6 and factorising if you like.

Why do you think your answer is wrong? What answer is given?

For c, w must be greater than 0. Who says that w can be 0?

It would help if you posted the answers that you are looking at since you seem to be basing what you're saying on these answers.

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Reply 2

coconut64

Original post by notnek

thanks

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Reply 3

Notnek

Original post by coconut64

thanks

Your answer for b) is the same as theirs. Have you tried simplifying it?

The answer for c) is wrong. It should be

x<2

.

You can easily check that their answer is wrong by plugging in e.g.

x=3

Reply 4

coconut64

Original post by notnek

Your answer for b) is the same as theirs. Have you tried simplifying it?

The answer for c) is wrong. It should be

x<2

.

You can easily check that their answer is wrong by plugging in e.g.

x=3

When I simpilify my answer it's still the not same though.

the two equations give me different answers when I sub 1.2 into x for both equations. This is physics and maths s tutor s solution though, are you sure it's wrong? Thanks.

Reply 5

Notnek

Original post by coconut64

When I simpilify my answer it's still the not same though.

the two equations give me different answers when I sub 1.2 into x for both equations. This is physics and maths s tutor s solution though, are you sure it's wrong? Thanks.

You should have 30 on the bottom not 300. Check that again - it should be an easy mistake to spot.

You can then multiply top and bottom of your fraction to make it have the same form as the answer.

The solution you posted is from the M1 solutionbank. It often has mistakes.

Reply 6

coconut64

Original post by notnek

Hi thanks I got the answer for b now but for part c it's w>0 so x<2? This is my answer .thanks

Reply 7

Notnek

Original post by coconut64

Hi thanks I got the answer for b now but for part c it's w>0 so x<2? This is my answer .thanks

That's correct.

The question actually says, "Deduce that x < 2".

So it's clear that there's a mistake in the solution.

Reply 8

coconut64

Original post by notnek

That's correct.

The question actually says, "Deduce that x < 2".

So it's clear that there's a mistake in the solution.

Thanks for helping. I was confused when I see the answer. I know that for this kind of question that mg is always bigger than 0 but I don't really understand why they can't be 0 though.

Reply 9

Notnek

Original post by coconut64

Thanks for helping. I was confused when I see the answer. I know that for this kind of question that mg is always bigger than 0 but I don't really understand why they can't be 0 though.

You are told that a particle of weight W is attached to the girder.

You can't have a particle with zero mass. Then it's not a particle anymore, it's nothing :smile: