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I'm rephrasing the question because it's part of a multipart question.

A skier with mass of 100kg starts at point A with a velocity of 31.3m/s. Find the skier's velocity at point B if the distance between A and B is 20m and a constant frictional force of 50N opposes his motion.

K=1/2mg

^{2}

v=√(v

_{0}

^{2}-2μ

_{κ}mgx

Those are the equations I thought relevant.

The first equation, K=1/2mg

^{2}is what I used to get the skier's velocity at A (previous part of the problem), which is 31.3m/s. 31.3m/s is correct; I have the answers.

Also, from the second equation, √(31.3

^{2}-(2x50Nx20m)/100kg))=30.98m/s ≈ 31m/s

I also know that 31 m/s is correct, because again, I have the answers. But I am particularly confused about why I divided by 100kg. I was trying to find a way to get rid of the "kg" in the Newton unit so I would have like units in both terms. Dividing by 100kg works to make the units match, but I don't understand if/why it works to get the right answer.

I appreciate any guidance. Thanks!