More Science Experiments
Every time an object moves on earth it is rubbing against something else; another object, the ground, a tabletop, etc. Whenever two objects rub against each other friction happens because objects are not slick. If you look at objects under a microscope they are actually very bumpy. When the microscopic bumps on objects rub together, friction happens and the object that is moving slows down and eventually stops.
Gravity holds objects on the earth and friction keeps objects from sliding all over the place. Zero gravity looks fun when astronauts get to float but zero gravity makes things difficult too. What if everything floated? We would be chasing objects all the time! Now think about what life would be like if there was no friction. You could just slide along the sidewalk with no effort at all, but it would be really hard to steer and stop, kind of like how it feels when you first learn to roller blade or ski. The wheels on roller blades help reduce your friction so that you can glide across the ground. It takes a lot less effort for your body to roller blade than it does for your body to slide your feet across the ground. Of course, it is also much easier to stop shuffling your feet than it is to stop on roller blades!
Do you know how to shuffle playing cards? You hold the card deck in one hand and then use your other hand to pull random numbers of cards off the bottom and put them on the top – an example is the blue card deck on the right. When you pull the cards up, it’s hard – because of friction. All of the cards are rubbing together. However, if you make a bridge, like the red card deck on the left, the cards easily fall back into place in one pile. When you make the bridge the cards bend so that less surface area of the cards is touching each other. Less touching=less friction.
You can test this another way. You will need 2 thick books. This experiment will show you just how influential friction can be. Phone books work great for this but any two thick books will do. Place the two books on a table. Push them apart – they slide across the table easily.
Now open the two books and slide them together so that their pages randomly each other. Now try to pull the two books apart. Can you?
This video will show you just how much strength it takes to pull two phone books apart. Friction is no small force!
Websites and Databases for Research:
- The Guardian: Phone Book Friction Factor
- Physics4Kids: Friction
- Sid the Science Kid: Fun With Friction
- Steve Spangler Science: Friction Fire
Science in Context: Friction is a database you can use in any IndyPL Library Branch or at home. Login using your IndyPL library card number. The Science in Context database will show you articles, images and videos to help you learn about bouyancy.
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