An electron is moving in a straight line with a velocity of 4.0×105 m/s. it enters a region 5.0 cm long where it undergoes an acceleration of 6.0×1012m/s2 along the same straight line. (a) what is the electron’s velocity when it emerges from this region? b) how long does the electron take to cross the region?

(a)

We can solve this part of the problem by using the following SUVAT equation:

where

v is the final velocity

u is the initial velocity

a is the acceleration

d is the distance through which the electron is accelerated

In this problem,

Solving for v,

(b)

The time needed for the electron to cross the region where it is accelerated can be found by using the following SUVAT equation:

where we have:

d = 5 cm = 0.05 m

Solving for t, we find: