# HELP PHYSICS! an electron moving along the x axis has a position given by... how far is the electron...?

An electron moving along the x axis has a position given by x = 17te-2t m, where t is in seconds. How far is the electron from the origin when it momentarily stops?

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- simplicitusLv 71 decade agoBest answer
This is pure math - no physics here at all.

the velocity v(t) is just the derivative of the position, x(t) with respect to time.

The electron stops when v(t) = 0. Given the t for which v(t) = 0, you can determine its position x(t).

To compute the derivative of x(t) = 17 t e^(-2t) use the basic rules you should already know.

d(uv)/dt = u v' + u' v

d(e^u)/dt = (e^u) u'

Note that the e^(-2t) can never be 0 and so can be factored out.

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