Unit 2 of 5 · SPH3U
Forces
Why does motion change?
Find every push and pull on a thing, add them, and predict whether its motion stays as it is or changes.
You can now describe how velocity changes. Next: what makes it change.
3 topics · 2 to play
What this unit covers
Newton's laws, friction, gravity — free-body diagrams that make the invisible pushes visible.
Topics
Topic 1: A book just sits on a table. What is pushing and pulling on it?8 ideas10 practice
- Idea 1, A push or a pull. Not started. Next for you.
- Idea 2, The touching test. Not started.
- Idea 3, The pull along a rope. Not started.
- Idea 4, How much stuff. Not started.
- Idea 5, Earth pulls everything. Not started.
- Idea 6, A perfect draw. Not started.
- Idea 7, Draw every force. Not started.
- Idea 8, The net arrow. Not started.
Ontario C2.1, C3.1, C3.4
Topic 2: You push a wall and nothing moves. So who is pushing whom?6 ideas11 practice
- Idea 1, Nothing needs a push to keep going. Not started.
- Idea 2, Change needs a net force. Not started.
- Idea 3, Which way it changes. Not started.
- Idea 4, Mass fights back. Not started.
- Idea 5, Every push is a pair. Not started.
- Idea 6, Pairs act on different things. Not started.
Ontario C1.1, C1.2, C2.2, C3.2, C3.3
Topic 3: Why does a heavy ball not fall faster than a light one?7 ideas13 practice
- Idea 1, The drag against the slide. Not started.
- Idea 2, The squeeze sets the price. Not started.
- Idea 3, It holds, then it slides. Not started.
- Idea 4, The leftover force. Not started.
- Idea 5, Heavy and light fall together. Not started.
- Idea 6, Why the feather lags. Not started.
- Idea 7, When the air wins. Not started.
Ontario C2.3, C2.4, C2.5, C2.6
The mental models this world builds
Each one is a card in the library, taught by one of the topics above.
- A force is a push or a pull between two things
- The touching test, then add Earth
- Balanced forces change nothing; the net force is what is left
- Motion needs no maintainer; only change needs a cause
- a = F ÷ m: force on top, mass underneath
- Every push is one half of a pair, on two different objects
- Friction is priced off the squeeze, not the speed
- Squeeze, drag, then the leftover to the second law
- Without air, every mass falls alike
What you will be able to explain
- List every force on an object with the touching test, and draw it.
- Say why a still book and a steadily sliding crate are the same case: balanced.
- Find the acceleration from the leftover force and the mass.
- Tell a third-law pair from a balanced pair by asking which object each arrow acts on.
- Price friction off the squeeze and explain why everything falls alike without air.
Kinematics described change; this world finds its cause. Forces are found first, so that nothing is missed. Newton's laws then say what the net force does. Friction and free fall are the two forces every real problem meets.
Labs and games
Pure play. Nothing here is recorded, ever.