A scanning electron microscope (SEM) accelerates electrons to very high speeds and fires those electrons at a sample. By looking at the way that the electrons interact with the sample, we can generate detailed images of objects we can't get with a traditional optical microscope, like mineral crystals or biological cells. To accomplish this goal, an SEM uses an accelerating voltage around 10kV (high voltage generally means better resolution). One such SEM uses an accelerating voltage of 13kV. How fast are the electrons moving after they pass through this accelerating voltage?

v = 1.697 x 10^8 ms^-1

Explanation:

As we know ½ mv2 = eV where m is the mass of electron = 9 x 10^-31 kg and v is the velocity or speed of electrons….

We have V = 13kV = 1.3 x 10^-14 eV

By putting the values…

v2 = 2 eV / m = 2 x 1.3 x 10^-14 / 9 x 10^-31 = 2.88 x 10^ 16 ms^-1

v = 1.697 x 10^8 ms^-1

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s