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## Homework Statement

A moving electron has kinetic energy K1 . After a net amount of work W has been done on it, the electron is moving one-quarter as fast in the opposite direction.

A) Find W in terms of K1

B) Does your answer depend o the final direction of the electrons motion? No

## Homework Equations

## The Attempt at a Solution

Hey guys so I learned how to solve this problem, but I dont really understand why they did what they did.

So in the problem they want to make everything in terms of K1

W= K2-k1

W=1/2mvf-1/2mvi

Here is where I get confused. The problem states that the electron is moving one quarter as fast in the opposite direction so wouldnt it be moving 1/4vf, and not 1/4vo?

For part B it was just yes or no, but I want to make sure I understand why it is no.

The reason why the answer does not depend on the final direction of the electrons motion is due to it being in terms of K1 and not in terms of K2.

Thank you