Idea 5of 6Builds onA push or a pull
Every push is a pair
You push a wall. Does the wall push you?
Today you'll discover
- what the wall does when you push it
- why the two pushes are exactly equal
- where a rocket gets its push in empty space
Think firstYour hand pushes a wall
You push a wall. Does the wall push you back?
Decide first, then press Next. Watch where each arrow starts.
Two labelled shapes side by side with a thin line where they touch. After a prediction, an arrow appears from the left shape pointing at the right one, then an equal arrow from the right shape pointing back. Both are shown together. The last step shows a rocket and its exhaust gas and asks what pushes the rocket.
See the whole ideathe big idea and the key word, in one place
The big idea
When one thing pushes another, the other pushes back equally.
Easy to get wrongThe truck does not push the car harder than the car pushes the truck. The forces are equal. The car changes more because it has less mass.
Key word
- third law
- Newton's third law: for every force one object exerts on another, the other exerts an equal and opposite force on the first
About this modelThe two arrows act on two different objects. They never cancel each other.
The two arrows act on two different objects. They never cancel each other.
Ready to use it?
- Name the partner force for a described push or pull, and the object it acts on.