If I am in a spaceship between earth and another planet and I throw a
quarter up in the air what would happen?  Where would the quarter go? 
I said it would fall toward me and my brother said it would stay
suspended because the force I exerted was greater than the mass I had
in space.  I said it would fall on me because I had the greatest mass
closest to it.

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Request for Question Clarification by supermacman-ga on 06 Feb 2004 21:59 PST

Suppose that you are far enough away from any massive celesial bodies
such that the assumption of true "zero gravity" is valid.

If you throw the quarter, it will fly away from you, and you will fly
away from it, such that the net momenta of both objects is zero
(conservation of momentium).

The gravitational attraction of the quarter to you will then pull both
objects (you and the quarter) together. However, due to the relatively
small mass of both the quarter and you, this attraction may take many,
many, many years or decades. (I can do a calculation, if so desired.)

- supermacman-ga

In microgravity, the quarter will continue in a straight line until it
encounters something to stop it. It will then rebound. In addition, if
you are not anchored to the floor, by Netwon's Third Law of Motion,
the act of throwing the quarter will cause you to fly away in the
opposite direction.

http://www.esa.int/export/esaHS/ESABYU0VMOC_astronauts_0.html

hlabadie-ga

The quarter will keep going forever, assuming it doesn't hit anything.
 It will not come back to the spaceship, for any ordinary spaceship,
and any ordinary throw.  The escape velocity the quarter must have to
leave the spaceship forever is given by v = sqrt(2GM/R) where G =
6.67E-11 is the universal gravitational constant, M is the mass of the
spaceship, and R is the radius of the spaceship.  If we pick numbers
that roughly represent a space shuttle-- M = 100,000 kg, and R = 5 m,
then v is a little more than 1 millimeter per second.  That means that
unless you "throw" the quarter as slow as a snail crawls, it will keep
going forever.

Racecar has got it right. To add something, that is your movement away
from the quarter. If you were floating in space next to a space ship
and tried to push the spaceship away from you, because the mass of the
spaceship is so much greater then your mass, you would move away from
the spaceship quite quickly but the spaceship would move very little.
Try pushing against a big rock. The rock won't move but you will keep
slipping backwards, right? Because the mass of the quarter is so much
less then your mass, the amount of opposite movement from you would be
miniscule. In fact you could probably measure it in fractions of inch
over hundreds if not thousands of years, depends on your mass.
Also to add something to hlabadie's comment. The rebound of the
quarter would depend on gravity.