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A charge in an electric field

An electron with a speed 5.00x10^8 cm/s enters an electric field of magnitude 1.00x10^3 N/C, traveling along a field line in the direction that retards its motion. (a) how far will the electron travel in the field before stopping momentarily, and (b) how much time will have elapsed? (c) If the region containing the electric field is .08m long, what fraction of the electron's initial kinetic energy will be lost in that region?

I need to understand how to set the problem up correctly in all parts of the problem, given the information in the problem.

Solution Preview

To start I would suggest bringing all the input data into the same system of physical units.
As two out of three numbers use meters( E = 1x10^3 N/C, L = 0.06 m), lets rewrite the starting speed as u = 5x10^6 m/s.

Next note that all the three questions deal with mechanical dynamics: speed, acceleration, kinetic energy. Therefore all we got to know about the electric field is what acceleration it causes the electron to have. For this we need to know the mass of the electron, m = 9.1x10^{-31}, and its electric charge, e = - 1.6x10^{-19}C.

Now, we know that the electric force is F = eE, and the 2nd law of Newton tells us how force and acceleration are related: ma = F.

So now we can take it all together to obtain the ...

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