Consider a 5 kg rock in free fall. It starts out from a height of 180 m with zero velocity, and hits the ground 6 s later, stopping abruptly.

Since the fall is due to its interaction with Planet Earth, we consider as our "system" BOTH of these objects - Earth and the rock.

For simplicity, assume Earth is also at rest at the beginning. Furthermore, assume "up" is in the direction away from the center of Earth, and counted as positive from here on.

Now calculate the momentum (including sign!) of BOTH the rock AND Earth at each of the following points in time:

a) Right at the moment the rock is released at 180 m height.

b) Right before the rock hits the ground

c) Right after the rock hits the ground.

d) What is the impulse imparted on Earth from before the Fall to the moment right before impact?

e) What is the impulse imparted on Earth from right before impact to the moment right AFTER impact?

f) What is the TOTAL (net) momentum of the entire system at each moment?