In terms of the earth-basketball system, the forces are "internal forces" so
no amount of "bouncing" will move the cm towards the sun.
Oren Quist, SDSU
-----Original Message-----
From: Gary Turner [mailto:turner@MORNINGSIDE.EDU]
Sent: Monday, December 29, 2003 11:58 AM
To: PHYS-L@lists.nau.edu
Subject: Basketball and Global Warming
A nice easy puzzle for the holiday season - I was reminded of this by the
recent conservation of (angular) momentum discussions. I have used it in
the past to demonstrate the problems of assuming linear momentum is only
conserved in "collisions" (whatever they are).
Consider a basketball, about to hit the ground. I has linear momentum
downward. A short while later, the ball will be moving up. It now has
linear momentum upwards. Where did the downward momentum go? Well that
one is easy, into the ground - but that means the ground is now moving
down.
Now, bounce a ball over and over, and eventually, the ground will start
moving down at an appreciable speed. This is where basktball and global
warming come in. Most basketball games are played at night. It does not
matter where on the world you are, night is always on the opposite side of
the Earth to the sun. So basketball games must be pushing the Earth
towards the sun - hence global warming.