Gravitation potential energy question help


by jbjohnybaker
Tags: earth, gravity, mgy, physics, potentital
jbjohnybaker
jbjohnybaker is offline
#1
Apr20-11, 07:22 PM
P: 19
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
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eczeno
eczeno is offline
#2
Apr20-11, 07:36 PM
P: 242
hello,

you have not accounted for the angle. the ski lift does not go straight up, it goes up a slope.
jbjohnybaker
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#3
Apr20-11, 07:42 PM
P: 19
Quote Quote by eczeno View Post
hello,

you have not accounted for the angle. the ski lift does not go straight up, it goes up a slope.
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
eczeno is offline
#4
Apr20-11, 07:45 PM
P: 242

Gravitation potential energy question help


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
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#5
Apr20-11, 07:49 PM
P: 19
Quote Quote by eczeno View Post
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.
is it right?

eg = (68.5)(sin13.5)(9.81)(2560)
eczeno
eczeno is offline
#6
Apr20-11, 07:50 PM
P: 242
looks good.
jbjohnybaker
jbjohnybaker is offline
#7
Apr20-11, 07:53 PM
P: 19
thank you very much.
eczeno
eczeno is offline
#8
Apr20-11, 07:58 PM
P: 242
cheers.


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