00:01
So in this question, we want to obtain the speed of the meteorite when it reaches the planet's surface.
00:07
We're told it starts at rest at a distance very far away, so enough to be taken as infinite.
00:13
We know the formula for kinetic energy is half mv squared and potential energy is minus the gravitational constant multiplied by the two masses over the separation.
00:23
So what we know is that the fact that the energy must be conserved from the initial state to the final state, such that the initial kinetic energy plus the initial potential energy must be equal to the final kinetic energy plus the final potential energy.
00:42
So we're told also that the initial kinetic energy is equal to zero and the distance at the beginning is taken to be infinity.
00:52
So as this tends to infinity here, you is going to tend to zero.
00:58
So from this, we can tell that, k1 plus k u1 is equal to 0.
01:08
So now we know that k2 plus u2 must also be equal to zero.
01:18
Now we can use these expressions here to sub in for k2 and u2.
01:24
So this is that half mv2 squared minus g m m.
01:40
Over r2 is equal to zero...