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Science Launch G4 / Week 04 / Wednesday
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Week 04 · Energy Converter

Wednesday

Investigation: Comeback roller
// Design a device that changes energy
⏱ about 15 min

Wednesday: Comeback roller

Rocket holds up a round cardboard canister. "I am going to build a roller that comes back by itself," he says.

Raven raises an eyebrow. "Back by itself? What do you notice inside your design?"

Rocket shows her a rubber band stretched from lid to bottom. A little weight hangs in the middle.

Nova peeks in. "Here is a hint," she says. "When the can rolls, the weight does not want to spin. What happens to the band?"

What you need

  • A round canister with a lid, like an empty oatmeal canister
  • One long rubber band
  • A small weight, like five large metal washers tied together with string
  • Two short pieces of a craft stick or pencil
  • Tape
Safety first
A grown-up pokes a hole in the center of the lid.
The grown-up pokes another hole in the center of the bottom.
Roll the canister on the floor, away from stairs.
Nothing goes in your mouth.

Steps

  1. Tie the weight to the middle of the rubber band.
  2. Push one end of the band through the hole in the bottom.
  3. Slide a stick piece through that loop and tape it down outside.
  4. Pull the other end through the lid hole. Hold it with the second stick and tape.
  5. Put the lid on. The weight should hang in the middle without touching the sides.
  6. Gently roll the canister away from you on a smooth floor. Watch what happens.
MAKE A PREDICTION
  • Read the question.
  • Tap your answer.
As the canister rolls away, the band twists up. What will happen when it stops?
RollHow far it rolled away (cm)How far it came back (cm)
Gentle push
Stronger push
While rolling away, motion energy was stored in the twisted ____.
When it rolled back, stored energy converted into ____ energy.

Where did the rest go?

Your roller probably did not come all the way back.

Some energy converted into sound as it rolled. Some became a little heat from rubbing.

Energy was not destroyed. It just went into forms that did not help the roller.

ROLLER THINKING
  • Read the question.
  • Tap your answer.
Why might a roller come back less far on a rug?
What stores energy inside the comeback roller?
StatementTrue or false?
The twisted band stored energy as the roller rolled.?
Some energy turned into sound as the roller rolled.?
The energy that did not help the roller was destroyed.?
WHY THIS EXERCISESome energy went into sound and heat, but none was destroyed.
Rubbing turns some motion into a little ____. Type one word.
WHY THIS EXERCISERubbing changes some motion into heat.

You built a real energy converter! Tomorrow we think like engineers about how to make it better.

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