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Force of Gravity

by thelightsare
Tags: gravitaional force, newtons law
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thelightsare
#1
Dec31-10, 04:18 PM
P: 9
1. The problem statement, all variables and given/known data
In this problem find the force of gravity of Al. Al is standing at the top of Mt. Everest at an elevation of 8,848 m. Al has a mass of 58 kg. The earth has a mass of 5.97e24 and a radius of 6.38e6m. What is the force of gravity acting on Al?


2. Relevant equations

F = GMm/r^2

3. The attempt at a solution
the dist. used to find F is from Al to the Earth's center ?
so r = 8848+6.38e6 ??????
then plug in values

F = G 58(5.97e24)/(8848+6.38e6)^2
F[tex]\approx[/tex]569.385 N?

Is this right? I feel like i'm missing soemthing
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PhanthomJay
#2
Dec31-10, 04:54 PM
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P: 6,038
Quote Quote by thelightsare View Post
1. The problem statement, all variables and given/known data
In this problem find the force of gravity of Al. Al is standing at the top of Mt. Everest at an elevation of 8,848 m. Al has a mass of 58 kg. The earth has a mass of 5.97e24 and a radius of 6.38e6m. What is the force of gravity acting on Al?


2. Relevant equations

F = GMm/r^2

3. The attempt at a solution
the dist. used to find F is from Al to the Earth's center ?
so r = 8848+6.38e6 ??????
then plug in values

F = G 58(5.97e24)/(8848+6.38e6)^2
F[tex]\approx[/tex]569.385 N?

Is this right? I feel like i'm missing soemthing
Hi, welcome to PF! Your equation is correct, but perhaps the values you are using are a bit off, since Al would weigh about 569 N at sea level, (more or less, depending on variabilities in earth's radius, etc), then he should weigh a wee bit less atop the Mount. But in terms of significant figures, essentially, he weighs pretty much about the same on top as he does at the bottom.
thelightsare
#3
Dec31-10, 05:01 PM
P: 9
Hi! Thanks you for the welcome and your help. And just for reassurance, for r was i right to add the two values together?

PhanthomJay
#4
Dec31-10, 06:32 PM
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Force of Gravity

Quote Quote by thelightsare View Post
Hi! Thanks you for the welcome and your help. And just for reassurance, for r was i right to add the two values together?
Yes, the distance apart is measured to Earth's center.
thelightsare
#5
Dec31-10, 10:34 PM
P: 9
Thanks so much!


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