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

Bike Shop Day

Bike Shop Day: The Ramp Test
// The rubbing force that helps a bike go and stop
⏱ about 15 min

Bike Shop Day: The Ramp Test

Rocket props a board on a stack of books. "Ramp ready!"

Raven lays out a towel, some paper and a piece of cloth. "What do you notice about each one?"

Nova hovers at the top of the ramp. "Keep the ramp the same every time," she says. "Change only the surface."

The family gathers to make predictions.

  1. Friction is a force between rubbing surfaces. It works against motion.
  2. Rough surfaces and harder pressing make more friction.
  3. Tread on tires and shoes makes more friction for better grip.
  4. Brake pads rub the rim. Friction slows the wheel.
  5. Friction makes heat and wears things out.
  6. Lubricants and rolling make friction smaller.
◇ THE RAMP TEST
Prop a board or big book on a few books. That is a low ramp.
At the bottom, lay one surface: bare floor, paper, cloth or a towel.
Let a toy car roll down from the same spot. Do not push it.
Measure how far it rolls past the ramp. Use a ruler or count foot lengths.
Try each surface three times. Keep the ramp the same height each time.
No toy car? Use a can or a ball. Or slide a small block and see if it moves.
Safety first
Keep the ramp low and steady on the floor.
Test in an open space, away from stairs and feet.
Pick up the surfaces after, so nobody slips.
For a grown-up
Ask your child to predict the order before testing.
Ask: was the result what you expected? What surprised you?
SurfaceTry 1Try 2Try 3
bare floor
paper
cloth
towel
RAMP TEST CHECK
  • Read the question.
  • Tap your answer.
In a fair ramp test, what should change?
A toy stops quickly on a surface. What does that tell you?
Grooves on a tire that help it grip are called what?
WHY THIS EXERCISETread makes more friction, so tires grip the ground.

Hooray for friction finders! Next week we look at wheels, tires and the air inside them.

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