- #1

SMA83

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## Homework Statement

Suppose the rod in the figure has mass m= 0.44 kg and length 26 cm and the current through it is I= 40 A.

**Part A:**If the coefficient of static friction is mu

_{s}= 0.45, determine the minimum magnetic field B

**(not necessarily vertical)**that will just cause the rod to slide. Give the magnitude of B.

**Part B:**Give the direction of B relative to the vertical (outwards towards us).

## Homework Equations

F=I*L*B*sin(theta)

F

_{friction}=F

_{n}*mu

_{s}

F

_{n}=m*g

## The Attempt at a Solution

This problem seemed straightforward until they mentioned that the magnetic field isn't necessarily vertical. I am able to plug in the numbers and calculate a solution with a vertical megnetic field, but when I have two unknowns (theta and B), I am not sure how to find the angle that would require the smallest value for B.

Note: There is already a thread based on a problem similar to this one here: https://www.physicsforums.com/showthread.php?t=303237. I didn't find the explanation sufficient to get me through the problem, however...I guess I'm a little slower than the guy in that thread. Thanks in advance for any help.