Gravitation potential energy question help

jbjohnybaker

1. The problem statement, all variables and given/known data

A 68.5-kg skier rides a 2.56-km ski lift from the base of a mountain to the top. The lift is at an angle of 13.9° to the horizontal. Determine the skier’s gravitational potential energy at the top of the mountain relative to the base of the mountain.

2. Relevant equations
Eg= mg delta y


3. The attempt at a solution

eg = (68.5)(9.81)(2560)
= 1720281.6 J

The answer in the textbook is 4.13x10^5 J :S

eczeno

hello,

you have not accounted for the angle. the ski lift does not go straight up, it goes up a slope.

jbjohnybaker

I have been taught that "the value of delta y is the vertical displacement of the object. This means that the horizontal path of an object follows in changing its vertical height is not significant" :S

eczeno

that is correct, but you have the wrong value for delta y. the lift travels a total distance of 2.56 km, but that is not the change in altitude, that is how long the cables are.

jbjohnybaker

is it right?

eg = (68.5)(sin13.5)(9.81)(2560)

eczeno

looks good.

jbjohnybaker

thank you very much.

eczeno

cheers.