* Friction is a force that opposes motion: When the marble rolls on the floor, the surfaces of the marble and the floor rub against each other. This creates friction, which acts in the opposite direction of the marble's motion.
* Friction converts energy to heat: The energy of the marble's motion is gradually transferred into heat energy due to friction. This means the marble loses kinetic energy (energy of motion).
* Decreasing speed: As the marble loses kinetic energy, it slows down. This decrease in speed leads to a lower average speed over time.
Think of it like this: If you push a marble across a smooth, frictionless surface, it would keep moving at a constant speed forever. However, in the real world, friction always exists, slowing the marble down.
