Visitors experiment with different mass distribution and see how this influences the wheels’ speed on an inclined plane.
Not all round objects roll at the same speed, even if they weigh the same. When the wheels roll down the rail, they start with the same amount of energy stored as height. When both wheels start turning the wheel with its mass at the rim uses a greater part of its stored energy to get rolling. Leaving less energy left for speed, so that the wheel with its mass at the center be faster.