Mackey

The Coin Heist

Mackey has a coin-heist challenge for you.

A coin is sitting on a card above a glass. Your mission is to get the coin inside the glass without touching the coin.

You get one quick move.

Can you work out what to move — and what the coin will do? Make your prediction before you try.

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MEET THE TEAM

Ages

5-12 yrs

Duration

min

10

Difficulty

Easy

Stage

Stage 1-3

Cite this resource

All Categories

Created by Darin Carr (BSc, DipEd)
NESA Accredited Teacher · Chemistry & Physics Specialist · 30+ years in-class teaching
Resource Version: 1.0
First Published:

Last Updated:

6 Sept 2025

14 Aug 2026

Experiments >

Forces, Motion & Balance

>

The Coin Heist

MISSION VERIFIED

Classroom tested. Teacher designed. Safe at home.

Practising NESA accredited

Australian Science Teacher

★ 30+ years of classroom experience

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Before you investigate... watch the mystery

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Mission Equipment

Gather your materials and get

ready for an amazing mission!

1 glass or cup
1 piece of stiff card
A small collection of coins — 5c, 10c, 20c, 50c, $1, $2 Australian coins work perfectly
A flat, stable surface — a table or desk

Let’s Investigate

Follow the missions steps below to solve the mystery.

1 Set up the heist

Place the glass on a flat, stable surface.
Lay the card across the opening.
Place one coin in the centre of the card, directly above the opening.
Don't move anything yet!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

2 Plan Your Move

Look carefully at the coin, card and glass.
You are allowed to move the card, but you cannot touch the coin.

Decide what kind of movement you think will work best.

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

3 Pull off the heist

Position your finger near the edge of the card.
Flick the card quickly and horizontally away from the glass.
Watch the coin carefully.

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

4 Stack the coins

Reset the card on the glass.
This time, stack two coins in the centre.
Predict: will two coins be easier, harder, or the same as one? Flick the card again. Now try three coins four etc

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

5 Mass test

Test the same experiment with different coins.
Try a 5c coin, then a $2 coin.
Which is easier to get into the glass — the lighter coin or the heavier one?

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

6 Slow flick test

Reset with one coin on the card.
This time, instead of a fast flick, slide the card slowly and steadily off the glass.
What happens to the coin this time — and how is that different from the fast flick?

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

1 Big Title

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

1 Big Title

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

1 Big Title

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

How could you get the coin into the glass without touching it?

1 Set up the heist

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

How could you get the coin into the glass without touching it?

1 Set up the heist

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

How could you get the coin into the glass without touching it?

1 Big Title

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

How could you get the coin into the glass without touching it?

The Crazy Scientist LAB Learning System™

Every experiment follows The Crazy Scientist Lab Learning System™ — a simple way to help kids think like real scientists.

LINK to what they already know,
ACTIVATE curiosity through hands-on discovery
BUILD understanding that actually sticks.

Have you ever been in a car that stopped suddenly — and felt your body lurch forward? Or slid forward on your seat on a bus when the brakes came on?

That feeling is your body trying to keep moving even though the vehicle has stopped. Your body wants to stay doing whatever it was already doing.

Objects are the same. Sitting still? Want to keep sitting still. Moving? Want to keep moving. They resist any change.
There is a coin sitting on a card, sitting on a glass. The coin is at rest. It wants to stay exactly where it is.

Predict: if you flick the card away very quickly, what will the coin do?

The card flew away — but the coin dropped straight into the glass. Think about the moment the card was moving: was the coin moving with it, or not?

When you tried the slow flick, the coin moved with the card instead of dropping in. What was different about the slow flick — and what does that tell you about what the coin was responding to?

The card had to push the coin to move it. In the fast flick, that push lasted a very short time. Was that enough time to get the coin moving? What does that tell you about how inertia works?
When you stacked more coins, the heist still worked. Did more mass make it easier or harder — and does that match what you predicted?

Newton's First Law says every object resists any change to its motion. The coin resisted moving sideways. The slow flick was long enough to overcome that resistance. The fast flick wasn't.

When a car crashes into a wall and stops instantly, the passengers keep moving forward. A seatbelt applies a force to stop them — but what would happen without one? How is this the same physics as the coin heist?

"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."

Think Like a Scientist

Scientists don't stop after their first discovery.

They ask new questions, collect more evidence and test their ideas in different ways.

Where could you take this investigation next?

Does the mass of the coin affect whether the heist works — is a heavier coin easier or harder to get into the glass than a lighter one?

Does the type of card affect the result — does a smoother card (like a playing card) work differently from a rougher card (like corrugated cardboard)?

Dr Puddledrip’s Science Tip

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Read the Science

Why did the coin stay while the card flew away?

The coin has inertia — objects resist changes to their motion. The coin starts at rest, so it tends to stay where it is.
When you flick the card, friction between the card and coin does push the coin sideways.
But the card moves away so quickly that friction acts for only a very short time. The coin barely has time to move sideways.
Once the card is gone, there is nothing supporting the coin, so gravity pulls it straight down into the glass.

Why does speed matter?

Pull the card slowly and friction has more time to act. The coin begins moving sideways with the card.
Flick the card quickly and friction acts for only a tiny amount of time. The card shoots away before the coin can move very far.
That's why a quick flick works better than a slow pull.
It's also the science behind the famous tablecloth trick — pull the cloth quickly enough and the objects on top barely move.

Does mass matter?

You might notice that different coins don't always behave exactly the same — but mass isn't the only thing that changes.
Different coins can also have different sizes, surfaces and edges, which can affect how they interact with the card.
A heavier coin has more inertia, but the friction force between the coin and card can also be greater.
That's why scientists don't rely on just one attempt. Repeat your tests and use your evidence before deciding whether mass really changed the result.

Real-World Connection

The Coin Heist might be tiny, but inertia is everywhere!

When a car suddenly stops, your body tends to keep moving forward. Your seatbelt provides the force that slows you down safely.
When a rocket blasts off, the rocket rapidly accelerates upwards while an astronaut's body resists that change in motion.
From a coin dropping into a glass to cars and spacecraft, the same basic rule applies: changing an object's motion requires a force.

Try next

• See inertia working against motion rather than in favour of stillness → [The Gravity Battlefield]

• Another experiment where a fast force does something a slow force cannot → [The Impossible Blow].

Teachers & Homeschoolers: Print-ready HD versions of this Science Behind It poster and companion G&T Challenge Card are available inside The Crazy Scientist LAB.

Scientist's Challenge

Designed for HPGE, gifted learners and children who enjoy an extra challenge.

Teachers & Homeschoolers: Print-ready HD versions of this Science Behind It poster and companion G&T Challenge Card are available inside The Crazy Scientist LAB.

The Next Question...

You've solved today's mystery. Now discover where curiosity can take you next.

What is inertia, really?

Inertia isn’t a force — it’s a property of matter. It describes how strongly an object resists any change to its motion.
The more mass an object has, the more inertia it has. That’s why a heavy coin is not harder to leave behind — it actually resists sideways motion even more strongly than a light one.

Newton’s First Law Around 1687

Isaac Newton described the principle that governs this experiment:

An object will remain at rest or continue moving in a straight line at constant speed unless acted on by an unbalanced force.

The coin is at rest. The only sideways force available is friction — and in a fast flick, friction acts for such a short time that it cannot change the coin’s motion.