# Homework Help: Linear acceleration in a uniform magnetic field due to torque

1. Jun 19, 2010

### astralboy15

Here the extra credit question I'm stuck on:

A square loop (perimeter of 4L and hinged along one side) is made of a wire that has a mass per unit length of 0.1000 kg/m and carries a current of 5.000 A. A uniform magnetic field of 10.00 mT directed perpendicular to the hinged side exists in the region. Determine the maximum linear acceleration magnitude, (a t) max , of the side of the loop opposite the hinged side.

My Question:
My teacher gave me a hint that torque = I*alpha, where I is the moment of inertia. How do I find the moment of inertia for this box? Then how do I work with angular acceleration to get the answer I'm after?

Thanks!

2. Jun 19, 2010

### graphene

What is the axis of rotation of the loop.

To find out I of the loop about this axis, you will need to find out the I's for each side of the loop about the axis and sum them.

$$\tau = I \alpha$$

$$a = r \alpha$$

You can see that a depends upon the torque and it is max when the torque is max.

When is the torque max?