Physics studies nature
Sciences that study nature are called natural sciences. Physics is one of them, along with chemistry and biology. Physics looks at the basic things: matter (what things are made of), energy (what makes things happen) and how they act on each other. The word comes from an old Greek word for nature.
Physics wants to answer questions such as: Why do things fall? Why is the sky bright in the day? How does a magnet work?
What is a phenomenon?
A phenomenon is anything that happens and can be seen, heard or measured. Rain, an echo, the rusting of iron and a boiling kettle are all phenomena. Physical phenomena are grouped like this:
- Mechanical: motion, falling, pushing (a ball dropping).
- Thermal: heat and temperature (a hot block, melting ice).
- Light: light, shadows, mirrors, rainbows.
- Sound: echo, music, vibrating strings.
- Electric and magnetic: lightning, a magnet pulling a nail.
Some phenomena are about big things (planets) and some about very small things (atoms). The same ideas are used for both.
How a physicist works
A physicist does four things again and again: observe a phenomenon, guess why it happens (a hypothesis), test the guess with an experiment, and write the rule in the language of maths. If the experiment disagrees with the guess, the guess changes. Nature always decides.
You can do this too: drop a pencil and a paper ball, watch which lands first, and then ask why.
Physics and other subjects
Subjects are not walls. They help each other.
- Maths: physics writes its rules as numbers and formulas, and uses graphs.
- Chemistry: atoms, bonds and reactions follow the rules of particles, energy and electric charge.
- Biology: your eye works like a lens, your heart is a pump and nerves carry electric signals.
- Geography: winds, ocean currents and earthquakes are explained with heat, pressure and waves.
- Technology: phones, bridges, cars and solar panels are built using physics.
Try it at home
Make a list of five phenomena you see in your house in one day. Write next to each: which group (motion, heat, light, sound, magnet) and one question starting with why.
Key formulas and definitions
- Phenomenon = anything that happens and can be observed
- Physics steps: observe → guess → test → write the rule (maths)
- Main groups: mechanical, thermal, light, sound, electric and magnetic
- Natural sciences: physics, chemistry, biology
Worked examples
1. Name the group of phenomena: a spoon gets hot in a cup of hot tea.
Thermal (heat). Heat moves from the tea to the spoon.
2. A magnet picks up pins from a table. Which group does it belong to, and is the magnet touching the pins at first?
Magnetic. The magnet pulls the pins from a small distance, before touching.
3. Why is a shadow longer in the evening than at noon? Which branch is it?
Light travels in straight lines. When the sun is low the rays reach the object at a slant, so the shadow is longer. It is a light phenomenon.
4. Give one way biology uses physics.
The eye lens bends light to make an image on the retina. The heart pumps blood like a pump. Both follow physics rules.
5. A student says: 'The earth is flat because it looks flat.' How would a physicist react?
A physicist would test it: watch ships disappear hull first, the shadow of the Earth on the Moon, and so on, and trust the evidence over the first look.
Common mistakes
- Thinking physics is only formulas. First comes watching and asking why; formulas come after.
- Thinking a phenomenon must be big or rare. A drop falling from a tap is a phenomenon.
- Believing a guess is true without testing it.
- Thinking subjects are separate: the same rules appear in physics, chemistry and biology.