What Is a Force? Contact and Non-Contact
In 2022, Kelsey-Lee Barber hurled a javelin 64.91 m to win gold for Australia — every centimetre shaped by contact and non-contact forces acting at once.
Printable Worksheets
Print or save as PDF — or build a custom worksheet from any module's questions.
Q1 · Push a door and pull a drawer open. What's the difference between pushing and pulling?
Q2 · Can one object affect another without touching it? Give an example from your life.
● Know
- The definition of a force and its unit (Newton)
- The difference between contact and non-contact forces
- Examples of each type of force in everyday life
● Understand
- Why forces are represented as arrows (vectors)
- How multiple forces can act on one object at the same time
- That all forces in daily life come from just 4 fundamental forces
● Can do
- Classify forces as contact or non-contact
- Draw a simple force arrow diagram with labels
- Identify forces acting on an Australian everyday object
When you kick a ball, something invisible happens in the fraction of a second your foot touches it. That invisible thing — a force — changes the ball's speed and direction. Forces are pushes or pulls.
Every force has two essential features:
- Magnitude — how big the force is, measured in Newtons (N)
- Direction — which way the force acts (up, down, left, right, forward, backward)
Because force has both magnitude and direction, it is called a vector. In diagrams, forces are drawn as arrows:
- Longer arrow = bigger force
- Arrow direction = which way the force acts
Forces can:
- Start an object moving (push a stationary ball)
- Stop a moving object (brakes on a bicycle)
- Change direction (turn a steering wheel)
- Change shape (squash a soft drink can)
The unit of force is the Newton (N), named after Sir Isaac Newton. A small apple weighs about 1 N. A school bag might weigh around 50–80 N.
Contact forces only work when objects are physically touching:
- Friction — opposes sliding motion between surfaces (e.g. your shoe gripping the floor)
- Tension — pulling force along a rope, string or wire (e.g. a tug-of-war rope)
- Normal force — the surface pushes back when you press on it (the chair pushing up on you)
- Applied force — a direct push or pull you apply with your hands
Non-contact forces act between objects that are NOT touching:
- Gravity — Earth pulls every object downward (the Moon is pulled by Earth's gravity even though they're 384,000 km apart)
- Magnetism — magnets attract or repel other magnets and magnetic materials from a distance
- Electrostatic force — static electricity on a balloon attracts small pieces of paper without touching
Australian context: a surfer at Bondi Beach has several forces acting at once — gravity pulling down, buoyancy pushing up, and water drag (friction) resisting forward motion — and none of them are "visible". That's the power of force diagrams: they make the invisible visible.
Here's a mind-blowing fact: every single force in the universe comes from just four fundamental forces. Scientists have been working on this since Newton's time.
| Fundamental force | What it does | Everyday example |
|---|---|---|
| Gravity | Attraction between any two objects with mass | You staying on the ground; the Moon orbiting Earth |
| Electromagnetic | Forces between electrically charged particles — includes magnetism, light, and ALL contact forces at the atomic level | Magnets; static electricity; friction at the atomic scale |
| Strong nuclear | Holds the protons and neutrons together inside an atom's nucleus | Nuclear power; the Sun's energy |
| Weak nuclear | Responsible for radioactive decay | Radioactive materials; carbon dating |
For Year 7 science, gravity and electromagnetic forces explain almost everything you'll encounter. The nuclear forces only matter inside atomic nuclei. When your desk "pushes back" on your book, that's actually electromagnetic repulsion between electron clouds — but we call it the normal force for simplicity.
A book sits still on a table. List all the forces you think are acting on the book. Are they contact or non-contact? What do you predict is special about how these forces compare to each other?
How close was your prediction?
Well done — you identified the forces and noticed they balance out.
Key insight: even still objects have forces acting on them — they just cancel out.
Below are 10 everyday forces. For each one, write whether it is a contact force (C) or non-contact force (NC), then name the specific force type.
| # | Situation | C or NC? | Force type |
|---|---|---|---|
| 1 | A rope pulling a water-skier | ||
| 2 | Earth pulling the Moon toward it | ||
| 3 | Your shoe gripping the footpath | ||
| 4 | A compass needle turning to face north | ||
| 5 | A chair pushing up on you as you sit | ||
| 6 | Static on a jumper attracting lint | ||
| 7 | A swimmer pushing off the pool wall | ||
| 8 | The Sun pulling Earth in its orbit | ||
| 9 | Air resistance slowing a falling leaf | ||
| 10 | A crane cable holding a load |
Draw a labelled force diagram of a person sitting in a chair. You should include:
- The person shown as a simple box or stick figure
- An arrow for gravity (label it with "Gravity" and a downward arrow)
- An arrow for the normal force from the chair (label it with "Normal force" and an upward arrow)
- Make both arrows approximately the same length to show they are balanced
After drawing (in your book or on paper), answer these questions here:
Q1. Name two contact forces and two non-contact forces acting on a skydiver before and after the parachute opens. (2 marks)
Q2. Explain why forces are drawn as arrows in science. What does the length and direction of the arrow tell you? (3 marks)
Q3. A ball is sitting still on a table. Name all the forces acting on it and explain why it doesn't move. (3 marks)
Answers
▾MCQ 1
B — A force is a push or pull. Weight is the effect of gravity, speed is motion, and stored energy is potential energy — none of these define what a force is.
MCQ 2
C — Gravity acts between objects without them touching. Friction, tension and normal force all require direct contact between objects.
MCQ 3
B — Arrow length represents magnitude (how big the force is). Length does not indicate speed, mass or direction change — the arrowhead shows direction.
MCQ 4
C — A fridge magnet uses magnetic force, which is a non-contact force. The magnet doesn't grip or tie — it attracts at a distance through its magnetic field.
MCQ 5
D — Friction is a contact force — it only acts when surfaces are touching. Gravity, magnetism and electrostatic attraction are all non-contact forces.
Short Answer 1
Model answer: Contact forces: air resistance/drag (fluid friction) and tension from the parachute straps. Non-contact forces: gravity (pulling the skydiver down throughout). Note: gravity acts before and after the parachute opens; air resistance increases dramatically after the parachute opens, creating a large upward drag force.
Short Answer 2
Model answer: Forces are drawn as arrows because forces are vectors — they have both magnitude (size) and direction. The length of the arrow represents the magnitude of the force (longer arrow = bigger force). The direction the arrowhead points shows which way the force acts (e.g., downward for gravity, upward for normal force). Using arrows lets scientists show multiple forces on the same object clearly and to scale.
Short Answer 3
Model answer: Two forces act on the ball: (1) gravity — a non-contact force pulling the ball downward, and (2) the normal force from the table — a contact force pushing the ball upward. The ball doesn't move because these two forces are equal in magnitude and opposite in direction, so they cancel each other out. The net (total) force is zero, so there is no change in the ball's motion — it stays still.
At the start of this lesson you saw the hook: a fridge magnet holding a note against a metal fridge without glue or string. Now you know what's going on — it's a non-contact magnetic force acting across a tiny gap!
How does your new understanding of contact vs non-contact forces compare to what you first thought? Name at least two other non-contact forces and explain what they all have in common.
- A force is a push or pull measured in Newtons (N). It is a vector — it has magnitude and direction, shown by an arrow.
- Contact forces (friction, tension, normal, applied) need objects to touch; non-contact forces (gravity, magnetism, electrostatic) act at a distance.
- All forces come from 4 fundamental forces — for everyday science, gravity and electromagnetic force explain almost everything.