# If I add more weights to a k'nex car at the top of a ramp, why does the distance traveled along the ground decrease after leaving the ramp?

Perhaps this is a gross oversimplification, but I thought the forces on the car could be simplified like this: Force(car) = Force(gravity) - Force(air resistance) - Force(friction).

Isn't the distance the car travels related to work and therefore force? I hypothesized the greater mass would result in a greater inertia and a greater force, so I thought the car would travel a further distance along the ground, but it consistently travels a shorter distance.

Is this because the greater mass causes more friction between the wheels and the ground, or is it more likely due to the additional air resistance of the weights sticking out of the car? Are there other forces I have not taken into account?

Any equations explaining my results would be appreciated.

• My guess would be increased friction between the axles and the body of the car, rather than between the wheels and the ground. Air resistance is probably negligible in either case (a rough calculation says it's about 5 orders of magnitude smaller than the force due to gravity). Commented Mar 31, 2017 at 16:40