Sputnik, the first artificial satellite to orbit the Earth, had a mass of 83.6kg and travelled at 7574 m/s. The radius of the earth is 6371 km and its mass is 5.972 x 10^24 kg. What gravitational force did Sputnik apply to the earth during this orbit?

Question

What I've got so far: so, I think it's possible to use either Fg=GMm/r^2 or Fc=mv^2/r, is that correct? I calculated the force to be 4,795,014,967 N which seems quite big to me and is incorrect. In that calculation, I used 6,949,000 m for r as Sputnik would have been orbiting about 578,000 m above Earth. Obviously I made a mistake somewhere.

Thanks in advance!

Answer 1

did your G have the right units?

you are correct that either equation should work

Fg = Fc ... in orbit ...

recalculate, and watch your units

Answer 2

Okay, I used Fc=mv^2/r and got 690.14 N. I used 83.6kg for m, 7574 for v, and 6,949,000 for r. Does that sound right?

Thanks.