# Pulleys/tension in a-level maths??Watch

#1
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!
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#2
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4 weeks ago
#3
(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?
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4 weeks ago
#4
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.
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#5
Thank you I think I get it now!
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4 weeks ago
#6
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.
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#7
Hold on, so when the tension is in the same direction as where the object is moving what do you do?
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#8
(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?
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#9
(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
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#10
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
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#11
Can someone help??
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4 weeks ago
#12
(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.
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4 weeks ago
#13
(Original post by Bluestudy)
Ok but what if the tension is in the same direction?
T-mg
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#14
No worries, got it now!
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