00:01
And this problem was asked about the energy needed to launch a satellite into a circular orbit at an altitude of 400 miles and 4 ,000 miles.
00:12
So because we have a circular orbit, we can use our convenient form of a body, the kinetic energy of a body orbiting another body in a circular orbit that is given by this expression here that we derived previously.
00:32
And our potential energy is the gravitational potential.
00:37
So our total energy is simply the sum of these.
00:42
So at any radius, r is then this.
00:45
So it's just minus 1 half, capital g, capital m, little m over r.
00:51
So in the first case, when we have, we wanna get the up 400 miles, then the radius is the radius of the earth plus 400 miles.
01:01
And so we can get that...