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## Homework Statement

The following picture illustrates the passage of an electron a magnetic field. The magnetic field is trying to reverse the electron's velocity to the opposite direction. Calculate the force that the magnetic field is exerting on the electron in given time of ## t = 5 ~\text{x} ~10^{-9}##.. You are given the period of time which all of this happened

## Homework Equations

## F = \frac{mv^2}{r} ##

## F = ma ##

## V = w r##

## w= \frac{2 \pi}/{T_Period}

## The Attempt at a Solution

I have used this way.

Magnetic field produces a force that is perpendicular to the velocity so it results in a circular motion

This reversing happen in half of a circle.

So

## w = \frac{\pi}{t} ##

Substitution of ## V = w r ## in ## F = \frac{mv^2}{r} ##

gives us

## F = m~ v ~w ##

Gives us the force

## F = 1.14~ \text{x}~ 10^{-15} ##

Now my friend used another way.

Which is ## F = m a ##

so ## F = m \frac{2v}{t} ##

which results in ## F = 7.28 ~\text{x} ~10^{-16} ##

However, this should be wrong because isn't this the net of all centripetal forces?

If I want the net of all of the magnetic forces I would use that equation

I translated the question, It isn't really clear of what it is asking for either the net force or the centripetal force. I just wanted to confirm the steps above

Thanks in advance.

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