Pre-Basic Physics

From Jonathan Gardner's Physics Notebook
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Things have mass. You can weight them on a scale and it will tell you how much they weigh.

Light things are easy to move about quickly. Heavy things require a lot of pushing just to move it a little bit.

Once heavy things start moving, they tend to keep on moving, unless something like the friction of the ground stops them, or something strong pushes on them.

In space, things keep moving without changing their direction or speed unless something pushes or pulls on them.

Gravity is the earth pulling things down towards it. Planets and the sun each pull on each other. Because the planets are moving, and the sun pulls on them, they orbit the sun. If they were moving too slow, they would be pulled into the sun. Too fast, and they would move away from the sun.

Work and Energy

If something is moving fast, it has a lot of energy. If it is heavy and moving fast, it has even more energy. Energy is a good measure of how much damage the thing will do when it hits something.

Energy is needed to do work, like moving a car, running the machines in a factory, etc...

Power is a measure of energy per time. Powerful things can make a lot of energy quickly.

The "power bill" you pay every month is really a measure of how much of the power company's energy you used up. If you don't run your computer, your blender, or your electric heater for a month, your bill will go down. If you're trying to run a factory from your home, your bill will go up.


Hot things are hot, cold things are cold.

Hot things that are very hot can burn you, but only if they are touching your skin or if you are very close to them.

Heat is the transfer of energy from hot things to cold things. It can happen in a vacuum (radiation), or through the air (convection), or through touch (conduction). Some things conduct heat better than other things. That's why even though a metal spoon and a wooden spoon are the same temperature, the metal spoon "feels" colder: more heat is conducted more quickly from your warm body to the spoon.

You can increase the temperature by increasing the pressure. You can lower the temperature by lowering the pressure. That's why your propane gas tank in your barbeque grill gets cold when you run the grill, and why it gets warm when you fill it back up.


Electricity conducts through metal, and doesn't conduct through plastic and wood very well. Sometimes, electricity can even jump through the air.

Large currents (usually due to large voltages) can kill you.

Magnets stick to each other, but if you align them a certain way, they repel.

You can create magnets by running a direct current through a wound wire.

You can create an electric motor using wound wire and a magnet.

Optics & EM Radiation

Light travels in a straight line. Lenses and transparent things can bend light. Prisms can separate light out into its component frequencies. Radio waves, like light, can bounce around or even through some things.

Quantum Mechanics

You may have heard that small things, like electrons and protons, behave strangely.