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Bike Shop 3-5 / Week 06 / Friday
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Week 06 · Patterns of Motion

Friday

Why rolling slows down
// Measure, find the pattern, predict
⏱ about 15 min

Friday: Why Rolling Slows Down

Rocket gives his toy car a push on the smooth kitchen floor. It glides a long way.

He gives it the same push on the rug. It stops quickly!

"Same car, same push," he says. "What happened?"

Raven kneels by the rug. "What do you notice about the two surfaces?"

Nova hovers low. "Something pushes back on a rolling wheel," she says. "Which surface pushes back more?"

Rolling resistance

A rolling wheel always meets some push against its motion.

This is called rolling resistance. It slows the wheel down.

A rough road is much harder to roll over than a smooth one.

Tires with low air on soft ground have more rolling resistance.

That is one reason a coasting toy slows down and stops.

SMOOTH OR ROUGH?
  • Read the question.
  • Tap your answer.
Where did Rocket's car roll farther?
What slows a rolling wheel down?
Which has more rolling resistance?

A slowing pattern

Here is a made-up practice test of a coasting toy car.

Each push was the same. Only the surface changed.

Surface (made-up test)Try 1Try 2Try 3
smooth floor200 cm195 cm205 cm
rug60 cm55 cm65 cm
About the made-up testTrue or false?
On the smooth floor, the car went about 200 cm each time.?
On the rug, the car went farther than on the floor.?
The results made a pattern we could use to predict.?
WHY THIS EXERCISEEach surface gave about the same result each try, so we can predict.
PREDICT THE NEXT TRY
  • Read the question.
  • Tap your answer.
Made-up test: predict a fourth try on the rug.
Made-up test: predict a fourth try on the smooth floor.
Try it
Roll a toy car with the same gentle push on two surfaces.
Mark where it stops each time with a small piece of tape.
Do three tries on each surface.
Safety first
Use a gentle push, the same each time.
Keep the rolling path clear of people and pets.
No toy car? Roll a can or a ball.
Surface (mine)Try 1Try 2Try 3
smooth surface
rough surface
A pattern is something that ____.
One wheel turn rolls one ____.

Super scientists! Tomorrow is Bike Shop Day. Measure a wheel and predict three turns with your family.

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