Hello ABV, I missed your replies so I'm a bit slow sorry.
The carts path length difference is about 6 inches (~15centimeters) with full path length 7 and 13 inches. Do you really think the standard deviation can cover this?
It may not be a random error. Can you reduce friction and see if the difference becomes less? Or even easier, increase friction and see if it becomes more. You're saying it should remain unchanged with small changes in friction.
The force for one object do whole work just for translational motion. However, the force for another object do work for rotational and translational motions.
Yes. A single force can be applied to several different things which all receive the entire force.
Base on 3-rd Newtons law force for translational motion of one object is equal to net force for translational and rotational motions of other object.
Yes, but the total force isn't the sum of the forces for translational and rotational motions. All 3 forces are the same (or rotational can be a bit less due to imperfections).
This is a good question. Do you realize one of the object just move, but on another cart moves and flywheels rotate on it. What force is rotating these flywheels? Where energy came from?
Again you're confusing force with energy. Two identical forces can transfer different amounts of energy. Work=force*distance. You can change distance to get different amounts of work (energy) from the same force. This is what you're doing.
