The Invisible Push & Pull — Grade 9 Forces

Set up your team

≈ 3 minutes

🎮 Mission briefing Your squad's mission: crack the mystery of the invisible push and pull — using real physics simulations as your testing lab. Groups of 4 (3 works too), one iPad per group. Test everything, guess nothing: evidence beats opinions in this game. Your progress saves on this iPad as you go, and the bar above tracks your mission stages.

Which class are you?

Group name (invent one!)

NavigatorDrives the sims — only changes things when the group agrees what to test.

RecorderTypes the group's answers. Checks everyone agrees first.

ChallengerAsks "how do we know?" — makes the group test it before typing it.

ReporterWatches the timer, submits the mission, speaks for the squad.

Part A — Sort it out

≈ 5 minutes · talk first, no sims yet

Talk through each situation as a group and tap your answers. Disagreements are good — argue it out, then test yourselves with the check button.

Situation	Push or pull?	Touching?	Name the force (if you can!)

The big idea That "touching / not touching" split is today's whole lesson: forces that need contact are contact forces; forces that act across a gap are field forces (non-contact forces).

Part B — Contact forces: the crate challenge

≈ 15 minutes

Experiment first, type after. The Challenger must see it happen on screen before the Recorder types.

PhET · Forces and Motion: Basics open full-screen ↗

B1. On the Net Force screen: set up a tug-of-war your team predicts will be a draw, then one where blue wins. Test both. What decides who wins? Write your rule in one sentence. B2. Now break the tie: what is the smallest change that makes blue win — and what was the net force? B3. Go to the Friction screen. Push the crate, then stop pushing. What does friction do to the moving crate? Then slide friction to none and push once — what happens now? B4. Friction and applied force are both contact forces. Using your experiments as evidence, write your group's definition of a contact force.

Part C — Field forces: action at a distance

≈ 15 minutes · about 7 per sim

Now for the strange stuff: forces that work without touching. Do both investigations.

C1 · Gravity — the invisible rope

PhET · Gravity Force Lab: Basics open full-screen ↗

C1a. The spheres never touch, yet the arrows show they pull on each other. Drag them closer, then apart. What happens to the force? C1b. Make one sphere as heavy as possible. Compare the arrow on the heavy sphere with the arrow on the light one. Anything surprising? Look carefully!

C2 · Static electricity — the clingy balloon

PhET · Balloons and Static Electricity open full-screen ↗

C2a. Rub the balloon on the jersey, then bring it near the wall. What does the balloon do — and what happens to the charges on each surface? C2b. The balloon is pulled in before it touches. What is your evidence that this is a field force like gravity — and not glue-like contact?

Fast finishers — the third field force Magnetism! Load the sim below, flip the magnet's polarity, and explain in your Snapshot how a compass "knows" which way to point without touching the magnet.

PhET · Magnet and Compass open full-screen ↗

Part D — Your Forces Snapshot

≈ 10 minutes · this is your exit ticket

Pull it all together as a group. Every row, no blanks — your own words, your own examples (South African ones score style points).

Force	Contact or field?	Our one-sentence definition	Real-world example
Applied (push/pull)
Friction
Gravitational
Magnetic
Electrostatic

★ Now answer the driving question in two sentences: How can something be pushed or pulled without ever being touched?

Part E — Reflect

last 5 minutes · each person adds a line E1. Which result surprised your group most today, and why? E2. Where did you disagree — and did you settle it by arguing, or by testing? E3. Field forces are invisible but run your whole day. Each person: name one moment in the last 24 hours when a field force acted on you without you noticing.

Complete your mission

Checking…

How to hand in (Reporter's job):
1️⃣ Tap Submit our answers — your squad's PDF report downloads automatically.
2️⃣ Open the Files app → Downloads → find your PDF (it's named after your squad).
3️⃣ Open Schoolwork → today's Forces assignment → upload your PDF. Done!

Then close the sims and return the iPad. Reporter: be ready with a 30-second debrief next lesson.