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Brrrrrraaaaa! The alarm clock awakens you. Do you leap out of bed in high gear, or do you bury your head under the pillow and go back to sleep? Whatever you do, you’re using energy.
Scientists define energy as the ability to get work done. You could be breathing, giving a party, building a pyramid, or even taking a nap.
But where is energy? You can’t touch it, but you can certainly see and hear its results. Energy is in the sounds and images your television produces. It’s also in the fuel that powers the vehicles that take you to different places. And it’s in the electricity that runs the gadgets and machines you use. Energy is in wind, waves, and sunlight, as well as in streams and rivers. There is definitely energy in you. And it’s in every other living thing, whether animal or vegetable. There’s even energy in a slingshot when you stretch the strap to its limit and then release it.
So what is this thing called energy, and where does it come from? Sit back, relax, and conserve your own energy, as we answer these questions and more about the fascinating world of energy... (Kids Discover)
▲ You can think of energy as something that can be stored; that’s called potential energy. A slingshot stretched to its limit has potential energy, or the ability to do work in the future.
▲ It’s also something that flows from one place to another, and that’s called kinetic energy. Once you let the elastic go, the flying stone has kinetic energy, or the energy of something in motion.
Review Questions - Set 1:
Review Questions - Set 1:
What is energy?
Give three examples of where you can find energy.
Define potential energy.
Define kinetic energy.
Most of the energy on Earth comes from the Sun. Without energy from the Sun, nothing could live on Earth—not people, animals, or plants. How much energy does the Earth get from the Sun? In just two weeks, the solar energy we get is equal to the world’s supply of coal, oil, and gas. ▶
Even the energy in moving water comes from the Sun! Sunshine heats up water and makes it evaporate from oceans and other bodies of water. This water vapor forms clouds. Eventually, the vapor condenses and falls to Earth as snow or rain, which forms rivers.
Energy Around Us
Energy Around Us
We use the concept of energy to help us describe how and why things behave the way they do. We talk about solar energy, nuclear energy, electrical energy, chemical energy, etc. If you apply a force to an object, you may change its energy. That energy must be used to do work, or accelerate, an object. We also speak of kinetic energy, potential energy, and energy in springs. Energy is not something you can hold or touch. It is just another means of helping us to understand the world around us. Scientists measure energy in units called joules.
Motion involves energy. Energy is the ability to cause change.
At the top of a hill, a roller coaster has potential energy – the energy stored in an object. As the roller coaster descends, its potential energy is converted to kinetic energy, the energy of movement.
An object in motion has momentum. An object’s momentum is its mass multiplied by its velocity. If its mass or velocity is large, an object will have a large momentum. The more momentum an object has, the harder it is to stop the object or to change its direction.
Review Questions - Set 2:
Review Questions - Set 2:
What is the unit of measure for energy?
What does it mean by the phrase: "Energy is the ability to cause change"?
How does momentum affect motion?
Active Energy vs. Stored Energy
Active Energy vs. Stored Energy
Kinetic and potential energies are found in all objects. If an object is moving, it is said to have kinetic energy (KE). Potential energy (PE) is energy that is "stored" because of the position and/or arrangement of the object. The classic example of potential energy is to pick up a brick. When it's on the ground, the brick had a certain amount of energy. When you pick it up, you apply force and lift the object. You did work. That work added energy to the brick. Once the brick is in a higher/new position, we would say that the increased energy was stored in the brick as PE. Now the brick can do something it couldn't do before; it can fall. And in falling, can exert forces and do work on other objects.
QUICK FACTS
QUICK FACTS
Energy is the ability to do work or cause change.
Energy is measured in joules
Everything around us has energy, but you only notice it when a change takes place.
Any time a change occurs, energy is transferred from one object to the next.
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