According to the Lorentz force law, an electron moving in a constant magnetic field follows a path which satisfies , where is a constant vector on . Prove that this path is a helix.

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- September 12th 2009, 11:30 AMmathman88Lorentz force law
According to the Lorentz force law, an electron moving in a constant magnetic field follows a path which satisfies , where is a constant vector on . Prove that this path is a helix.

- September 20th 2009, 01:54 AMKiwi_Dave
We can choose to align the z axis with the magnetic field B. Then:

, ,

So:

Solving the third equation by integrating twice with respect to t: where k is a constant.

Now if you differentiate the second equation and then substitute for from the first then you will get:

which has the general solution:

So

Now using equation 1

So

Now using , , we can write:

This is the equation of a helix.