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Everyday Machines / Week 12 / Thursday
4/6
Week 12 · The Elevator and Your Machine Show

Thursday

Test the counterweight
// A car, a counterweight and your big explanation
⏱ about 15 min

Thursday: Test the Counterweight

Rocket puts a toy in the cup. The cup drops! "Oops!"

Raven asks, "What do you notice about the bag now?"

"The bag is too light," Rocket says.

Nova glows. "Would you like a hint? Change one thing and test again."

A fair test

Today we change only one thing: the coins in the bag.

Everything else stays the same.

Then we see how easy the cup is to lift.

  • Your cardboard elevator
  • A small toy to ride in the cup
  • Extra coins and tape
  • Paper and a pencil
Safety first
Coins stay in a sealed bag, away from younger siblings and mouths.
A grown-up opens and seals the bag.
Keep the string off necks and fingers.
  1. Put the toy in the cup.
  2. Take all the coins out. Lift the cup by the string. Hard or easy?
  3. Write it in your table.
  4. Ask a grown-up to put a few coins in the bag.
  5. Lift the cup again. Hard or easy?
  6. Add a few more coins. Test again.
  7. Find the number of coins that makes the cup almost float.
Coins in the bagHow the cup felt to lift
None
A few
More
WHAT HAPPENED?
  • Read the question.
  • Tap your answer.
With no coins, how did the cup feel to lift?
What happened as you added coins?
What was the one thing we changed?

Too much counterweight

What if the bag is much heavier than the cup?

Then the cup flies up and the bag drops.

Real elevators have a brake that holds the car still.

The counterweight is made about as heavy as the car.

SentenceTrue or false?
A fair test changes only one thing.?
More coins made the cup harder to lift.?
The counterweight is made about as heavy as the car.?
WHY THIS EXERCISEA balanced counterweight makes the car easy to move either way.
A FAIR COUNTERWEIGHT TEST
  • Tap a card.
  • Then tap its spot.
1First
2Next
3Then
4Last
For a grown-up
Open and seal the coin bag yourself each time.
Ask: what would happen with a heavier toy in the cup?
Praise careful testing, even when the cup drops.
Draw your test. Show the cup and the bag at their best balance.

You tested a counterweight like an engineer. Super!

Tomorrow, we learn what keeps an elevator safe.

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