Re: Physics Answer to a Question...

[palmer@sfu.ca (Leigh Palmer)]

> Is this correct?  Any help would be greatly appreciated.  If it is wrong,
> could you please tell me where I went wrong?

Dwight, you've got the simpler version of the rocket problem here. The
difficulty you are having arises from the fact that you are not taking
into account the fact that grampa is moving when he spits. Thus the
value of V2 you are using is too high; it should be 4.5 m/s since that
would be the average speed of the lungers with respect to the rest
frame over the duration of this ugly process.

The problem is much more interesting if you don't let the old guy
drink. Then you have the classical rocket problem, a much more
interesting one. Add gravity and your students will be working at
first year university level. Besides, with that fellow's habits I
doubt he would be drinking water anyway. He's probably into the Jim
Beam.

Leigh