### Author Topic: Retardedly Poor Physics Problem  (Read 2158 times)

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#### Nate

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##### Retardedly Poor Physics Problem
« on: March 02, 2008, 01:35:07 AM »
It took me an hour just to read it right, I am not even sure how to solve this, its for NON calculus based Physics 2.  Its for my friend and I am too lazy to look at my Physics book...I think Digital Logic replaced physics in my brain.

http://img89.imageshack.us/img89/4348/jiggawiggawi8.png

#### dark_drake

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##### Re: Retardedly Poor Physics Problem
« Reply #1 on: March 04, 2008, 12:08:40 AM »
My physics 2 is a bit rusty, but here goes:

First draw a free body diagram.  We know that the weight must equal the tension, T, times cos(30). The Force from the magnetic field on the wire, F, must equal T*sin(30).

Now, we know that F=I*L x B.

The force must be to the right, so, using the right hand rule, we now know that the current is coming toward us. Furthermore, the magnetic field is perpendicular to the direction of current, which makes the cross product just L*B*sin(90).

With all that, we can write our equations and solve for T and then I.
Forces in Y:
W=cos(30)*T.
0.22kg/m * 1m * 9.8 m/s^2 = cos(30)*T
T=2.49 N

Forces in X:
I*(L)*(B) = T*sin(30)
I*1m*0.52T=2.49N*sin(30)
I=2.39A
errr... something like that...