Idea 2of 8Builds onA push or a pull
The touching test
How do you find every force on something?
Today you'll discover
- a test that finds every force
- why the floor's push counts
- the name for a surface's push
Think firstA hand pushes a crate along a floor
Which of these push or pull on the crate?
Decide first, then press Next. Count the touches, then add Earth.
A box on a floor with a dot at its centre. After a prediction, arrows appear one at a time: Earth's pull straight down, the floor's push straight up, the hand's push to the right. The surface's upward arrow is then named. The last step hangs the box from a cord and asks whether a surface pushes on it.
See the whole ideathe big idea and the key word, in one place
The big idea
What touches it can push or pull it. Then add Earth.
Compare themThe floor pushes the crate up. The crate's motion does not push anything. A force needs a thing on the other end.
Key word
- normal force
- the push a surface gives an object pressing on it, square to the surface
About this modelArrows are forces, not motion: a box can move with no arrow pointing its way.
Arrows are forces, not motion: a box can move with no arrow pointing its way.
Ready to use it?
- Run the touching test on a described object and list its forces.