If you were give an uknown mass and told to find it's mass w/out using a scale, how would u go about doing it. You have a meter stick, stopwatch, and 2 cars (which you can mass) w/ flat surfaces so you can put the unknown weight on it. I want to use the conservation of momentum in elastic collisions to figure out the unknown mass, but how would I go about incorprating the friction into it? any other info. would also be very helpful. Thanks.