Friction

The best part about living in Vermont is that we get to experience all of the seasons. Sometimes cool weather appears out of nowhere and we don’t have the proper attire so we rub our hands together to warm them up. Ever wonder why this works? The answer is friction! Friction is a force that acts between two objects that are in contact with one another. It slows or stops movement between the two surfaces that are touching. Friction happens all of the time between all kinds of objects. Rough surfaces will cause more friction than smooth surfaces. More friction means that the object will have a greater resistance to movement. When you rub your hands together, the action of scraping the surface of your skin back and forth against each other causes the molecules in your skin to move a little faster. When molecules move faster to overcome friction, energy is released and the temperature goes up. The friction caused by rubbing your hands together makes them feel warmer. Give friction a try on your own with this easy experiment!

Materials: Dry rice, pencil, bottle

Directions: Fill the bottle with rice. Take the pencil and put it in the rice, moving it around. Try to take the pencil out – does it come out easily? Put the rice back to normal so there is no pencil hole and stick the pencil in again. Move the pencil up and down gently and tap it on the table a few times. Try to take the pencil out – what happens differently this time? Be patient and keep trying.

How it works: You are creating friction between the pencil and the rice! When you put the pencil in the bottle initially, there is less friction. This means that you can pull the pencil right out of the bottle. But when you put the pencil in a second time and tap the bottle on the table a few times, the rice settles against the pencil and the edges of the bottle. More rice is touching and pushing against the pencil when it is settled. This creates greater friction between the rice and the pencil, allowing you to pick up the bottle full of rice by only holding the pencil.

Want more? Research it!: How would you walk in a frictionless world?