# Effects of firing shells on the Earth's angular momentum

During a certain war, millions of shells were fired by country A towards the west, and even more shells were fired back by country B towards the east. The average momentum of each bullet were the same on average. What was the ultimate effect on the angular momentum of Earth?

Here's my try: B fired more bullets than A. Because average momentum of each bullet is the same, there must be a net change in momentum. As such the Earth's angular momentum would have to change.

However, the answer was that there was no effect, not even a very slight one. Why is that so?

• This is homework, so I'm not going to answer. I'll instead give a hint, in the form of another question: What happens to the shells? – David Hammen Jul 3 '14 at 3:27
• If they were fired into orbit you would have an interesting problem. – C. Towne Springer Jul 3 '14 at 3:37