# Cant understand this line in the book(semiconductor nightmare 4)

in the marked red line
how they comeup with the fact the the velocity increases by this amount
?
i didnt see this expression before in this book

tiny-tim
Homework Helper
how they comeup with the fact the the velocity increases by this amount
Hi nhrock3!

F = ma = m(dv/dt) …

In this case, F = qE = -eE, so m(dv/dt) = qE, so ∆v = -eEt/m.

thanks :)