Physics work question

Practice Question Solving
1

The total mass of a skier is 60.0 kg. He starts from rest and slides down a slope without exerting any effort. After he has descended through a total vertical displacement of 50.0 m, he is travelling at a velocity of 30.0 m/s.
How much work has been done against resistive forces experienced by the skier as his velocity increases from 0 to 30.0 m/s?
[Take the gravitational field strength g as 10 N/kg.]

A 3000J
B 30000J
C 27000J
D 57000J
E 2700J

I got the final answer 54000J from w=fxd = 600x90, but it says A. Why?

2

Hi, i got 30000J for W = Fd = mgh = 60 * 10 * 50 = 30000J……

3

I got E = mgh = 30,000 J as Winter got
Then E=1/2mv^2 = 27,000 J

30,000 - 27000 = 3000J

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4

Thank you for your help! But can I ask why you’re subtracting instead of adding?

5

Well im assuming that the G Potential Energy at the top is converted to the Kinetic Energy down the slope - in an ideal system this conversion is 100%, all the GPE converted to KE , but in this case as theres a difference between these two figures, im taking that as the work done/energy consumed by resistive forces.

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