# physics

Two wires are made of the same material. The first wire dissipates power P with a current of I. If the second wire is 3 times as long and has twice the diameter, what will the current need to be through the second wire to dissipate the same power P as the first wire?

A particle enters a magnetic field with velocity v. Find the mass of the particle in terms of v, B, and x.

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1. Using the idea of resistors in series and in parallel, we conclude that:

resistance is proportional to length, and
inversely proportional to the area.

That should be sufficient to solve the first problem.

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posted by MathMate

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