I am reading a book about general physics kinematics, optics, waves, etc.(adsbygoogle = window.adsbygoogle || []).push({});

It focuses more on history than on explaining equations or sample problems.

One of the sample problems in Electric Fields section asks to find energy and speed when a positron moves from one plate that has electric potential of 1e6 V to another that has zero electric potential.

As far as the energy is concerned it is the potential which equals

U=1e6 x 1.6e-19 = 1.6e-13 which is what the answer is at the back of the book states.

But for the speed I get a different answer.

I assume that potential is turned in to kinetic as positron reached the other plate so:

Ek=0.5mvv

then v=sqr(2Ek/m)

m=9.1e-31 Kg

Ek=1.6e-13

so from above v=5.9e8

but in the book the answer is 1.4e7m/s

What am I missing or not understanding?

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# Electric fields problems

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