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Bike Shop 3-5 / Week 03 / Monday
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Week 03 · Friction: Grip and Slip

Monday

The force that rubs
// The rubbing force that helps a bike go and stop
⏱ about 15 min

Monday: The Force That Rubs

Rocket slides a book across the table. It glides, then stops. "Hey, I did not tell it to stop!"

He pushes it the other way. It stops again.

Raven leans in. "What do you notice? It stops both ways."

Nova hovers just above the table. "Look where the book touches the table," she says. "Something happens there."

Rocket opens his shop notebook.

What is friction?

Friction is a force between two surfaces that touch and rub.

Friction works against motion.

Push a book to the right. Friction pulls back to the left.

Push the book to the left. Now friction acts to the right.

That is why a sliding book slows down and stops.

A ball rolling on the ground also stops after a while.

FRICTION CHECK
  • Read the question.
  • Tap your answer.
Rocket pushes a book to the right. Which way does friction act?
Where does friction happen?
Why did Rocket's book stop sliding?
What force works against motion when two surfaces rub?
WHY THIS EXERCISEFriction is a force between rubbing surfaces that works against motion.
StatementTrue or false?
Friction works against motion.?
Friction only happens when things move to the right.?
A rolling ball stops after a while because of friction.?
Friction is a force.?
WHY THIS EXERCISEFriction works against motion in any direction.
Try it
Slide a book gently across a table, one way and then the other.
Watch it slow down and stop each time.
Write in your shop notebook which way you pushed and which way friction acted.
Safety first
Slide the book gently. Keep it on the table.
Use a soft-cover book, and keep fingers out of the way.

Friction on a bike

A bike has many places where surfaces touch.

The tires touch the ground. Your shoes touch the pedals.

Your hands touch the handlebars.

This week we find out where friction helps and where it gets in the way.

In your shop notebook, draw a bike. Circle three places where two surfaces touch.

Fantastic noticing! Tomorrow we find out why some surfaces make more friction than others.