Interactions Over Small and Large Distances
Some forces need objects to touch, and some reach across empty space. Learn the difference between contact and non-contact forces, the three forces that act at a distance, and the idea of a field.
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Forces near and far
A force is a push or a pull on an object. Some forces only work when two objects are touching, but others can reach across empty space. This module looks at that difference, at the three forces that act at a distance, and at how they reach from the tiniest scales up to the whole Solar System.
Contact and field words
Four terms run through this topic. Learn them first.
Touching or not?
Every force is either a contact force or a non-contact force.
Match the term
- Force
- Contact force
- Non-contact force
- Field
- A push or a pull on an object
- Acts only when objects are touching
- Acts at a distance, without touching
- A region where a non-contact force acts
Contact or non-contact?
A magnet attracts a paperclip across a small gap, without touching it. Which kind of force is this?
- A non-contact force
- A contact force
- Friction
- Air resistance
The three forces that reach across space
There are three non-contact forces. The gravitational force acts between any two masses and always pulls them together. The magnetic force acts between magnets and magnetic materials. The electrostatic force acts between electric charges. For magnets and charges, like repels like and opposite attracts.
Match the force to the example
- Gravitational force
- Magnetic force
- Electrostatic force
- Contact force
- Keeps the planets orbiting the Sun
- Makes a compass needle point north
- Makes a rubbed balloon stick to a wall
- Acts when a book rests on a table it touches
Non-contact forces
Which TWO of these are non-contact forces? Choose all that apply.
- The gravitational force
- The magnetic force
- Friction
- Tension in a rope
From small to large
Put these interactions in order by the distance over which they act, from the smallest to the largest.
- Forces holding atoms together, over tiny distances
- A magnet attracting a nearby paperclip
- Gravity pulling an object down to the ground
- Gravity holding the planets in orbit around the Sun
Contact and non-contact forces
A push or a pull on an object is a _____. Friction acts only when objects touch, so it is a _____ force. Gravity acts without touching, so it is a _____ force. The three non-contact forces are gravitational, magnetic and _____. A region where a non-contact force acts is called a _____.
Spot the non-contact forces
Tap the TWO non-contact forces.
- The gravitational force
- The magnetic force
- Friction between two surfaces
- Tension in a rope
Which force?
Which non-contact force acts between two electric charges?
- The electrostatic force
- The gravitational force
- The magnetic force
- Friction
Contact or non-contact?
For each interaction, decide whether it is a contact or a non-contact force.
- A book rests on a table, pressing down on the surface it touches. Which kind of force is this?
- The Moon is held in orbit by the Earth, with nothing touching between them. Which kind of force is this?
- Two north poles of magnets push apart without touching. Which kind of force is this?
Explain the forces
Explain the difference between contact and non-contact forces, and how a field lets a force act at a distance.
- Explain what a contact force is, with an example
- Explain what a non-contact force is, and name the three of them
- Explain what a field is and how it lets a force act without touching