Force (Can someone check what I did wrong)

[Josh123]

Can you tell me what I did wrong.

I posted it on photobucket:

http://img.photobucket.com/albums/v228/LianaBlank/img003.bmp

 

[arildno]

Could you magnify it a bit?
It is difficult to read the text.

 

[Josh123]

Well, it's a little bigger, but still kind of small

http://img.photobucket.com/albums/v228/LianaBlank/cc5a5559.bmp

Basically, I know that
I = 5 A
B= 0.5 T
the sides of the loop are 0.05 m long
The loopp was rotated around the Y axis and makes a 60 degree angle with the X-Y plane

I must find the Force on side A-B.

My answer (0.0625) is 1/2 of the correct answer (0.125).

 

[Doc Al]

If the B field is in the + z direction, then what's the angle between that B-field and side a-b? It's not 60 degrees!

 

[Josh123]

I used 30 degrees (angle between B and A-B)... Is that correct?

 

[Doc Al]

I used 30 degrees (angle between B and A-B)... Is that correct?

No, it's not. (For some reason I thought you used 60 degrees... sorry about that!) Hint: the line A-B is parallel to the Y-axis.

 

[Doc Al]

I used 30 degrees (angle between B and A-B)... Is that correct?

Note that 30 degrees is the angle that the plane of the loop makes with the B-field. It is not the angle between the B-field and the line segment A-B!

 

[Josh123]

Oh ok. It's at 90 degrees from B then. That makes more sense. Basically, the side that is 30 degrees from B is the bottom wire right?

Thanks for your help

 

[Doc Al]

You got it.