The radius of the Earth is approximately 4000 miles. If Sputnik I (the first satellite) roughly weighs 184 lbs on the surface of the Earth, find the amount of work W (in mile-pounds) required to launch it into orbit at an altitude of 139 miles.
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The work necessary is equal to force x distance.
However, in this problem, the force is not constant since it will change depending on the height of the satellite. Consequently, we will need to use integrals to calculate the total work.
W = F x d
F = (GMm / r^2)
We will simplify GMm into a general proportionality constant, k.
F = (k / r^2)
At the surface of the Earth (r = 4000 mi), the satellite weighs 184 lbs. Therefore
184 = k / (4000)^2
k = (184)(4000)^2
The distance, d, is given by r
lower limit of integration: 4000
upper limit of integration: 4139
integrand: F x d = ( (184)(4000)^2 / r^2 ) x r
10^8 mile-pounds of work.