00:02
A 1 ,940 kilogram satellite is put into a circular orbit about the earth.
00:06
We are given that the radius of the orbit is 12 ,600 miles, and we want to find the kinetic energy of this satellite in circular orbit.
00:17
Here i've drawn a diagram of the satellite orbiting earth, and i've indicated the radius of orbit, which is from the satellite to the center of the earth.
00:27
To find the kinetic energy, we first have to find the velocity.
00:30
And to do that, let's use a force equation.
00:35
So here, in circular orbit, the centripetal force is equal to the gravitational force, and we're using centripetal force because it is in circular motion.
00:49
The satellite is in circular motion.
00:52
So centripetal force is mv squared over r, and gravitational force is big g, m1, m2 over r squared.
01:01
And actually i'll get rid of this one on the first m here on the right because these two ms are the same.
01:10
So here we will go ahead and manipulate the left side such that it looks like kinetic energy.
01:22
And we can do that by multiplying r on both sides and multiplying one half on both sides so that we get mv squared on the left and one half g m.
01:34
M2 over r.
01:37
And now this side is kinetic energy...