The Motion of Charged Particle in Electric Fields Problem

[Freeq]

3. Two electrons are fired at 3.5x10^6 m/s directly at each
other.
(a) Calculate the smallest possible distance between the
two electrons.
(b) Is it likely that two electrons in this situation will actually
get this close to each other if the experiment is
performed? Explain your answer.

Hello, let's look at question 3(a). I just did that question, but I got different answer than the one in the book.
There is the book solution is in the attachment.

I'm concerned about a mistake in the formula. I think that there is no square in r. Even two pages after, you can see that there is no square there. How is this Possible?

 

[tiny-tim]

Hi Freeq!

I'm concerned about a mistake in the formula. I think that there is no square in r. Even two pages after, you can see that there is no square there. How is this Possible?

Yes, you're right.

The dimensions there are completely wrong (and the units at the end combine to m^1/2, not m).

energy = qV = Fr = kq₁q₂/r not kq₁q₂/r²

(which book is this?)​

 

[Freeq]

Nelson 12 Physics. It looks like they used formula for electric force, but not energy. However, I still think it is a good book.