Forces and Changes to Earth's Surface: Year 4 Study Guide
Pushes and pulls make things move, and forces also shape the land.
A force is a push or a pull. Forces can make an object start moving, stop, change speed or change direction. Contact forces need touching, such as a push, pull or friction. Non-contact forces act at a distance. They include gravity (pulls objects towards Earth), magnetism (magnets attract some metals such as iron) and static electricity (rubbing a balloon on your hair).
Forces also change the planet. Rain, wind, waves and rivers wear away rock and soil, while earthquakes and volcanoes build and break the surface quickly.
Types of forces
| Force | Type | Effect |
|---|---|---|
| Friction | contact | slows moving objects, creates heat |
| Gravity | non-contact | pulls objects down |
| Magnetic | non-contact | attracts or repels magnets |
| Air resistance | contact | slows things moving through air |
Investigating forces
A fair test changes one thing, measures one thing and keeps all else the same. To test friction, roll a toy car down a ramp over different surfaces (carpet, tile, sandpaper) and measure how far it goes. The rougher the surface, the more friction and the shorter the distance.
Which surface has the most friction?
The surface.
Same car, same ramp height.
Record three trials.
Changes to Earth's surface
Slow changes include weathering and erosion by water, wind and ice. Fast changes include flooding, bushfires, volcanoes and earthquakes. Australia's Great Dividing Range, Uluru and the Murray River show different landforms shaped over a very long time. People change the surface too, by building roads, mining and farming, and can also reduce damage by planting trees and protecting riverbanks.
Worked example and common mistakes
Example: A ball thrown up falls back because of gravity. Common mistakes: thinking heavy objects always fall faster than light ones in a vacuum, mixing up magnets attracting only some metals with attracting all metals, and not repeating a test. Look for patterns after at least three trials.
Check your understanding: model answers
1. For example, friction (contact) and gravity (non-contact). 2. Ice has less friction. 3. Slow: erosion by a river. Fast: an earthquake or flood.
✨ Key Takeaways
- A force is a push or a pull.
- Gravity and magnetism act at a distance.
- Friction slows things down.
- Both slow and fast events change Earth's surface.
💬 Questions for Discussion & Reflection
- Name a contact force and a non-contact force.
- Why does a car slide further on ice than on gravel?
- Give one slow and one fast change to Earth's surface.
Print a science experiment report →