# The Official Mechanics 2B Thread, AQA, 29 January 2009Watch

9 years ago
#41
for question 3.
when you have F=ma, you times the whole of a through by m(7) first, then use pythagoras to end up with F=15N.
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9 years ago
#42
sooo what did you get for the radius? please show method for what you did...
thanks
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9 years ago
#43
(Original post by Mathlete91)
sooo what did you get for the radius? please show method for what you did...
thanks
I got 0.322m for the radius and used:

T sinx=mv^2/r

v=wx r

v^2=w^2 x r^2

T sinx=m ( w^2 x r^2 ) /r

Tsinx/m=w^2 x r

r=(Tsinx/m) divide by w^2

Not sure if its correct, but my friend used another way and he ended up with the same answer
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9 years ago
#44
(Original post by SuperStaaaR)
I got 0.322m for the radius and used:

T sinx=mv^2/r

v=wx r

v^2=w^2 x r^2

T sinx=m ( w^2 x r^2 ) /r

Tsinx/m=w^2 x r

r=(Tsinx/m) divide by w^2

Not sure if its correct, but my friend used another way and he ended up with the same answer
YAY OMG I thought I had got that wrong and accidentally included mg but I hadn't! Yes I did F = mr(w^2) Because w^2 is a but thats basically what you did Cheers (++rep)
x
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9 years ago
#45
anyone need any help with any question?
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9 years ago
#46
(Original post by Mathlete91)
YAY OMG I thought I had got that wrong and accidentally included mg but I hadn't! Yes I did F = mr(w^2) Because w^2 is a but thats basically what you did Cheers (++rep)
x
Np, hope were right though
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9 years ago
#47
anyone have the answers to the mechanics jan 09 paper?

thanks....bit stuck on question 7 and 9
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