Physics question

[00tec]

Taking your problem as presented, and with your assumption that no other forces (friction, air resistance, etc...) are applied, then the balls would be subject to Newton's first law of motion, also known as the law of inertia. Both objects would maintain their initial velocities (20mph) and neither would ever stop or slow down, as no other forces are acting upon them. This is what Mr. Prena said.

If we slowly step back from the idealized world, the first factor to come into play is force. It takes more force to get the 20 pound bowling ball up to the same velocity (20 mph) then the 15 pound ball. It will therefore take more force to stop the 20 pound ball. This represents the concepts of conservation of energy and momentum. One of the first forces to act against the balls will be rolling resistance with the surface. Assuming the coefficient of friction between both balls and the hard surface is the same, then it will take more exposure to the force of friction over time to make the heavier ball come to a stop. Thus, the heavier ball will roll further.

If you start adding in other factors, such as air friction, or movement up inclined planes, or surface elasticity, you start changing the sum of forces acting on the balls, and you can contrive a situation where either ball rolls farther.

Agree.

If you have 2 identical vehicles, with one containing extra weight (but had the exact same rolling resistance), and you were traveling 60mph, then let off the gas, the momentum of the heavier vehicle carries it further.