### Q21(c) 2009 HSC

Posted:

**Wed Jul 07, 2010 11:03 am**Hello Prof Joe,

I've been wondering about this question for a while... Here's the paper: http://www.boardofstudies.nsw.edu.au/hs ... hysics.pdf

There are two approaches to what you could take.

1) Use F=BIL and then use F=mg and solve for B.

2) Halve the torque found in part (b) and use it in T=nBIA and then solve for B.

I know why the 1st approach works but I'm not sure why the 2nd approach would work. Why does it work?

Thanks

I've been wondering about this question for a while... Here's the paper: http://www.boardofstudies.nsw.edu.au/hs ... hysics.pdf

There are two approaches to what you could take.

1) Use F=BIL and then use F=mg and solve for B.

2) Halve the torque found in part (b) and use it in T=nBIA and then solve for B.

I know why the 1st approach works but I'm not sure why the 2nd approach would work. Why does it work?

Thanks