Where is the Effect of the Equal Opposite Reaction?
Most recent answer: 06/20/2013
- Brian (age 24)
Champaign, IL USA
Brian- I bet that question is one that lots of people wonder about.
Say you gave the pen a little push East. It pushes back on you West. While it's heading East, shouldn't you head West? You should, but since you're much more massive than the pencil you pick up much less velocity. Even worse, you're pretty firmly connected to the Earth, and you and the Earth together are much, much more massive than the pen. So yes, you and the Earth will head West but not enough to notice.
One way to look at this is to describe Newton's third law as conservation of momentum, mv, where m is mass and v is the velocity vector, including direction. You can see that canceling the momentum of a small mass one way requires much smaller v for a big mass going the other way.
Mike W.
(published on 06/20/2013)