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Science Launch G3 / Week 01 / Tuesday
2/6
Week 01 · Balanced or Not?

Tuesday

Balanced forces
// Pushes, pulls and what they do
⏱ about 15 min

Tuesday: Balanced Forces

Rocket and Raven hold opposite ends of a jump rope. They pull hard, but nobody moves.

"We are stuck in the middle!" Rocket laughs.

"What do you notice about our pulls?" Raven asks.

Nova circles the knot in the middle of the rope. "Compare the size of each pull," she says. "Then compare the directions."

Rocket grins. "Same size, opposite ways. I think I see it!"

Forces that cancel out

Sometimes two forces push or pull on one object at the same time.

When the forces are the same size and point in opposite directions, they are balanced.

Balanced forces cancel each other out. The motion of the object does not change.

A still object stays still. That is why the rope knot stayed in the middle.

  • Two friends push a box from opposite sides, equally hard. The box stays put.
  • Two teams pull a rope with the same strength. The rope does not move.
  • You press your hands together, equally hard. Your hands stay still.
BALANCED OR NOT?
  • Read the question.
  • Tap your answer.
Two teams pull a rope equally hard in opposite directions. What happens?
Balanced forces are the same size and point which way?
Balanced forces are the same ____.
Balanced forces point in ____ directions.
If the forces on a still box are balanced, does the box move? Type yes or no.
WHY THIS EXERCISEBalanced forces do not change motion, so a still box stays still.
For a grown-up
Press palms with your child, matching their push.
Ask: what happens when we push equally? What happens when one of us pushes harder?

Spot the balance

Balanced forces are all around you, even when nothing moves.

A book sits still on a table. Gravity pulls it down. The table pushes it up just as hard.

The two forces are the same size and point opposite ways. So the book stays put.

WHICH ONE IS BALANCED?
  • Read the question.
  • Tap your answer.
Which one shows balanced forces?
Two kids push a door from opposite sides with equal force. What does the door do?
In tug of war, one team pulls harder. Are the forces balanced?
StatementTrue or false?
A book on a table has balanced forces.?
Balanced forces always make things speed up.?
Balanced forces point in opposite directions.?
If one pull is bigger, the forces are still balanced.?
WHY THIS EXERCISEBalanced forces cancel out, so motion stays the same.
TUG OF WAR FROM START TO FINISH
  • ?The rope moves toward the stronger team.
  • ?Both teams grab the rope.
  • ?The rope stays still.
  • ?One team pulls harder.
  • ?Both teams pull equally hard.
WHY THIS EXERCISEEqual pulls are balanced. A bigger pull makes the forces unbalanced, so the rope moves.
What word means forces that cancel each other out?
WHY THIS EXERCISEBalanced forces are equal and opposite, so they cancel out.
Try it
Press your two palms together in front of you.
Push equally hard with both hands. Do your hands move?
Now push harder with your right hand. Which way do your hands go?

You spotted balanced forces! Tomorrow you get to test them yourself with a box and two strings.

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