### Rearranging formulae

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Messages: 1 - 3 of 3
• #### Message 1.

Posted by U15708662 (U15708662) on Sunday, 26th May 2013

Hi,

I'm struggling to rearrange the formula in some questions, could you possibly talk me through how to rearrange these formulae?

E = I (R+r) - Trying to find r

V = U + at - Trying to find t

Vo = -Rf / R1 x V1 - Trying to find V1

Thanks

• #### Message 2

, in reply to message 1.

Posted by U15737416 (U15737416) on Sunday, 26th May 2013

Hi,

I'm struggling to rearrange the formula in some questions, could you possibly talk me through how to rearrange these formulae?

E = I (R+r) - Trying to find r

V = U + at - Trying to find t

Vo = -Rf / R1 x V1 - Trying to find V1

Thanks
Hi ok so how I normally think about it is what you do to one side you have to do to the other. So for your first formula to find r you first need to get rid of I. Therefore to get rid of I you mus divide that side by I. So as I said what you've done to one side you have to do to the other meaning that you are left with E/I= R+r then you subtract R from the left hand side and your left with r. So the equation becomes r = E/I + R. Try using this to see if you can get the other ones. If not just let me know

• #### Message 3

, in reply to message 2.

Posted by BitesizePhysicsTeacher (U15165682) on Sunday, 26th May 2013

If you struggle with rearranging the symbols, then substitute the numbers in first and try to simplify them before rearranging.

If you rearrange wrongly you'll be penalised, and might not get any marks.

If you write the form of the equation in the data book, then substitute in the numbers you'll get half of the marks!

If you then rearrange wrongly, you've still got half the marks!

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