What would happen if you tried to slide across the cement in your tennis shoes? You probably wouldn’t move much and you might even trip, right? What if you tried to slide across a wooden floor wearing only socks? Or slide across a sheet of ice in your boots? You’d probably slide right along. Why is it easier to slide across ice or a wooden floor than cement? The answer is (drumroll, please): FRICTION. Friction is a force that holds back movement of an object – in this case, you. The rougher a surface, the more friction.The smoother a surface, the less friction.
- Liquid smooths out a surface, creating less friction. For example, it’s harder for a car to stop on a wet road than a dry one because the water creates a barrier between the car and the road. The tires don’t have as much contact with the road.
- Oil in a car engine lubricates the parts so they experience less friction. Friction causes heat, which can damage a car engine.
- When one object rubs or slides against another, it slows down. The energy is changed from moving (kinetic) energy to heat energy. When you rub your hands together, for example, your hands get warm.
- Friction: The resistance that occurs when two objects move against each other.
- Barrier: Something that prevents movement.
- Lubrication: To apply an oily substance to reduce friction.
Question and Answer
Question: Can we predict how much friction will occur between two objects?
Answer: Yes. Several things determine how much friction there is. First, the rougher something is the more friction it will create. Try rubbing your hand over sandpaper. It’s hard to do, right? Now rub your hand over a piece of smooth paper. Less friction! How much force is used also determines friction. If you push hard on your bike pedals, you create more friction – and slow down more quickly – than if you press lightly. The weight – or mass – of an object also determines friction. Try blowing a feather across a table. Easy, right? Now try blowing a rock of the same size across the table. The rock has more mass, which creates more friction and makes it harder to move.
Head over to Mocomi to watch a short video about friction.