The world is a fascinating place. From the colors of leaves to how birds fly, there’s always something new to explore. What you may not realize is that a special field of science called physics helps explain how a lot of things in the world work. Physics explains how things move and how different kinds of energy can affect these things. Once someone understands the rules of physics, it’s possible to understand how the whole universe works!
A tree in a field may not look like it’s going anywhere, but it, like everything else in the universe, is actually in motion. Motion simply means whether an object is moving or not. If two friends throw a ball back and forth, that ball is in motion. The tree in the field is actually in motion through space, traveling around the sun along with the rest of the planet.
All motion comes from a force acting on an object. A basketball is put in motion when a player’s arm and hand pushes the ball. If the player rolls the basketball along the ground, this is called a simple movement, since the object (the ball) is moving in only one direction. If the player throws the basketball through the air, the movement becomes complex, since the ball will go up, forward, and down again. There are many different ways that force can be applied to an object. For instance, even if a basketball hasn’t been touched, the normal force of gravity is keeping it from floating off into space.
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Energy is everywhere. It’s what makes objects hot or cold, and it’s what provides the force necessary to move an object. Thermodynamics is a branch of physics that studies how energy works. One form that energy can take is heat. When a pot of water is boiled on a stove, the energy transfers from the gas or electricity in the stove to the pot and the water, heating them. In the same way, when liquid water is put into a freezer, the heat contained in the water transfers to the surrounding air, and the water freezes as more of its energy leaves.
Many kids already know that the sun, light bulbs, and lightning all produce light. What they may not know is that light is actually a type of energy! When light waves hit an object, they react in different ways. When they meet a polished surface, like a mirror, they reflect right back where they came from. When they can travel through an object, like a piece of ice or a glass of water, they refract, which means that they change direction as they pass through something.
Refracted light waves can make things look weird, since the light waves get bent or bounced around in a different direction from where they entered the object. A good way to see refraction at home is by filling a clear drinking glass with water and putting a straw in it. When looked at from the side, the straw will look like it’s been broken! In reality, the straw is still in one piece, but the light is playing tricks on your eyes.
Electricity can do big things, like power a television or turn on all of the lights in a city, but the things that make up electricity are very, very small. Atoms are the tiny little things that make up all matter in the universe. In these atoms are different particles called protons and electrons. Protons have a special kind of energy called a positive charge, while electrons have a negative charge. When these particles interact, the result is electricity! Magnetism happens when all of the electrons of an object, like a piece of metal, spin in the same direction.
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No physics lesson would be complete without mentioning gravity. Gravity is the force that holds everything onto the ground, but everything on Earth has a gravitational force, too! The reason that the ground pulls a falling apple down instead of the apple pulling the ground up is thanks to the fact that Earth is bigger and heavier than the apple. That’s also why the gravity of the sun keeps Earth in an orbit instead of the other way around. Farther out in the universe, gravity helps explain how stars are formed and how the Milky Way galaxy stays together. No matter where you look in the night sky, gravity and physics are there!.