Phone book friction : Fizzics Education

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# Phone book friction

### You will need:

• Two softcover books of the same size. The more pages the better! We use old phone books as we’re less concerned if the pages get damaged, plus the soft covers make it easier to get the books together.
• Two people to demonstrate

1

Open the covers of each of the books and lie one cover on top of the other as shown.

2

Begin to layer alternate pages of each book on top of each other. The aim is to get as much contact between the book pages as possible – take your time and do as many pages as you can in the time you have!

3

Keep going until both books are weaved together. You may need to push the two book spines towards each other to keep the books together.

4

Get your two volunteers to hold the book spines or at least the corners of the books.

5

Moment of truth! Hold the spines as tight as possible and try to pull the books apart. If you have set the books up correctly you’ll find that this is very difficult!

6

#### Get the Unit of Work on Forces here!

• Push, pull
• Friction & spin!

From inertia to centripetal force, this unit covers many concepts about Newton’s Laws!

Includes cross-curricular teaching ideas, student quizzes, a sample marking rubric, scope & sequences & more

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### What is going on?

This demonstration is all about friction! Friction occurs when two surfaces touch each other. The more contact between two surfaces, the more friction. Friction as opposes movement. This means the higher the friction between two surfaces, the harder it is for those surfaces to slide along each other.

By weaving as many books pages as possible together, the two books had a lot of surface area of pages touching each other and so there was a lot of friction between the book pages. Because there was a lot of friction between the books, you need to apply a lot of force to separate the books!

You would have found that the books were much easier to separate wiggle the pages to move the pages apart. Often in the classroom the only reason that the books separate is that the volunteers pull the books side to side & up and down as well as backwards. This wiggling reduces the contact between the book pages and you’re able to separate them. Under controlled conditions, it is much harder to separate the books than you might expect.

The Mythbusters tested this with two tanks and measured the forces involved!

In Todd Sampson’s Life on the Line, he took this to another level by bungee jumping with phone books connected (not an experiment to replicate!).

Tyres keep you in contact with the road. This contact gives you more friction and allows you to be able to quickly brake your vehicle or change direction. Always keep your trees in good condition and with tread to be able to disperse water so that you can remain in contact with the road… you need that friction!

### Variables to test

More on variables here

• Try different size books.
• Does glossy paper vs standard paper make a difference?