Final answer:
Option D, which includes both rolling a skateboard on different surfaces and having students rub their hands together, is the best way to demonstrate friction by showing its effects on speed and heat generation. It provides a clear and practical understanding of kinetic and static friction.
Step-by-step explanation:
The best way to demonstrate friction would be option D, as it involves both A and B, showcasing friction in different contexts. In A, rolling a skateboard down the sidewalk and then on the grass would clearly show how friction affects speed.
On the sidewalk, the skateboard rolls smoothly because there's less friction, while on the grass, higher friction slows the skateboard down, illustrating how kinetic friction affects motion. Option B, where students rub their hands together rapidly to observe heat production, demonstrates another effect of friction: it can generate heat due to the force of resistance between surfaces.
Understanding friction also comes from observing everyday phenomena. For example, take the case of pushing a piece of chalk across a chalkboard that results in a screeching sound.
This happens because of the rapid alternation between slipping and sticking due to the difference between static and kinetic friction. A similar process occurs when tires screech on the pavement, often heard during sudden stops or sharp turns.
Friction plays a significant role in everyday life, affecting everything from transportation to simple activities like walking. Knowing about friction can help us predict how quickly objects will slow down or understand why certain movements produce heat.
Therefore, exercises involving demonstrations of friction's effects, such as Option D, are excellent practical ways to experience and understand the concept.