Force of Gravity

thelightsare

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

PhanthomJay

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

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

Yes, the distance apart is measured to Earth's center.

thelightsare

Thanks so much!