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Pulleys/tension in a-level maths??

Hi everyone, just need some help with mechanics?
How do you know when calculating the tension whether to do T - force or force - T ? If you need an example q so this makes more sense let me know!
Reply 1
Avatar for Bluestudy
Bluestudy
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Please help?
Reply 2
Avatar for Notnek
Notnek
21
Original post by Bluestudy
Hi everyone, just need some help with mechanics?
How do you know when calculating the tension whether to do T - force or force - T ? If you need an example q so this makes more sense let me know!

It depends which direction you take as positive. Your question makes me feel like you're not thinking about the directions properly.

Can you please post an example question and show us the part of working where you get confused?
Reply 3
Avatar for meme259
meme259
9
depends which way the object is moving/trying to move. take this direction as the positive value, and then subtract any forces going in the other direction.
Reply 4
Avatar for Bluestudy
Bluestudy
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Thank you I think I get it now!
Draw all the forces acting on the objects. Then look at which way the system will accelerate/which way the question is asking for. Then take away all the forces going against from the direction for.
Reply 6
Avatar for Bluestudy
Bluestudy
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Hold on, so when the tension is in the same direction as where the object is moving what do you do?
Reply 7
Avatar for Bluestudy
Bluestudy
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Original post by fedfan18
Draw all the forces acting on the objects. Then look at which way the system will accelerate/which way the question is asking for. Then take away all the forces going against from the direction for.

Ok but what if the tension is in the same direction?
Reply 8
Avatar for Bluestudy
Bluestudy
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Original post by Notnek
It depends which direction you take as positive. Your question makes me feel like you're not thinking about the directions properly.

Can you please post an example question and show us the part of working where you get confused?


Ok I’ll post an example
Reply 9
Avatar for Bluestudy
Bluestudy
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Here’s the question I don’t get, it’s part a I and ii, I just don’t get how you know which way round the T goes
Reply 10
Avatar for Bluestudy
Bluestudy
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Can someone help??
Reply 11
Avatar for Notnek
Notnek
21
Original post by Bluestudy
Here’s the question I don’t get, it’s part a I and ii, I just don’t get how you know which way round the T goes

I can't see the question.
Original post by Bluestudy
Ok but what if the tension is in the same direction?

T-mg
Reply 13
Avatar for Bluestudy
Bluestudy
OP
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No worries, got it now!

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