Discover Potential and Kinetic Energy All Around You

Energy is the ability to do work or cause a change. You use energy every time you move, and energy is stored all around you in stretched rubber bands, food, and objects sitting high above the ground.

In this topic, you will explore two main types of energy: potential energy (stored energy) and kinetic energy (energy of motion). Understanding these forms connects directly to Energy Conversion: Transformations Between Forms, which you will study next.

Potential energy is energy that is stored in an object and ready to be released later. It depends on an object's position, height, or shape.

There are three types of potential energy you should know:

• Gravitational potential energy stored because of an object's height above the ground. A ball at the top of a tall hill has more gravitational potential energy than one at the bottom.
• Elastic potential energy stored in a stretched or compressed object, like a stretched rubber band or a compressed spring.
• Chemical potential energy stored inside molecules, like the energy in food that your body uses to run and play.

The higher an object is, and the heavier it is, the more gravitational potential energy it has. A heavy rock at the top of a tall cliff has much more potential energy than a feather near the ground.

Kinetic energy is the energy an object has because it is moving. Any object that is in motion has kinetic energy.

Two things affect how much kinetic energy a moving object has:

• Speed the faster an object moves, the more kinetic energy it has.
• Mass the heavier a moving object is, the more kinetic energy it has at the same speed.

A bicycle moving rapidly down a road has kinetic energy. A soccer ball rolling across a field has kinetic energy. An object sitting still has no kinetic energy at all.

Potential energy and kinetic energy can convert back and forth into each other. This is called energy conversion.

When a ball rolls down a hill, its gravitational potential energy decreases and its kinetic energy increases. When a ball is thrown upward, its kinetic energy converts back into potential energy as it rises and slows down.

Think about a roller coaster: at the top of a hill, it has the most potential energy. At the bottom, it has the most kinetic energy. A pendulum works the same way it has the most potential energy at the highest points of its swing and the most kinetic energy at the lowest point.

You will explore this idea further in Energy Conversion: Transformation Between Forms.

Energy: Energy is the ability to do work or cause a change. You use energy every time something moves, heats up, or changes.

Kinetic energy: Kinetic energy is the energy an object has because it is moving. Any moving object a rolling ball, a flying bird, a running person has kinetic energy.

Potential energy: Potential energy is stored energy based on an object's position, height, or shape. It is energy that is held and ready to be released.

Stored energy: Stored energy is another way to describe potential energy. It is energy that is being held in an object and has not yet been released to do work.

Motion: Motion is the act of changing position. Kinetic energy is the energy that comes from motion if something is moving, it has kinetic energy.

Gravitational potential energy: Gravitational potential energy is stored energy that depends on how high an object is above the ground. The higher and heavier the object, the more gravitational potential energy it has.

Energy conversion: Energy conversion happens when one type of energy changes into another type, like when potential energy becomes kinetic energy as a ball rolls downhill.

Speed: Speed measures how fast an object is moving. The faster an object moves, the more kinetic energy it has.

Height: Height is how far above the ground an object is. Height is the key factor in gravitational potential energy the higher the object, the more stored energy it has.

Elastic potential energy: Elastic potential energy is stored energy in a stretched or compressed object, like a rubber band or a spring. When released, it converts into kinetic energy.

Chemical potential energy: Chemical potential energy is stored energy inside molecules, like the energy in food or a battery. Your body uses chemical potential energy to move and grow.

Object at rest: An object at rest is not moving. An object at rest has no kinetic energy, but it may have potential energy depending on its position or shape.

You can practice identifying potential and kinetic energy by looking at everyday objects. Ask yourself: Is this object moving? If yes, it has kinetic energy. Is it still but in a high position or stretched shape? If yes, it has potential energy.

Try thinking about a skateboarder on a ramp. At the top, the skateboarder has gravitational potential energy. As they roll down and speed up, that energy converts to kinetic energy. At the bottom, kinetic energy is at its greatest. This connects to what you will learn in Types of Energy: Mechanical, Electrical, Chemical.

You have already learned important ideas that connect to this topic. In Work and Force: Mechanical Advantage, you explored how forces cause objects to move. In Energy Loss: Energy Transfer Efficiency, you learned that energy changes form as it moves through a system. In Energy Transfer: Producer to Consumer Flow, you saw how energy moves from one place to another.

You also studied Heat Sources: Natural and Artificial Sources, Heat Transfer: Conduction, Convection, Radiation, Unbalanced Forces: Net Force and Motion, and Balanced Forces: Equal Opposing Forces. All of these ideas help you understand how energy behaves and changes.

This topic connects to many other important science ideas. Here is how they all fit together:

• Energy Flow: Food Webs and Energy Transfer You will see how energy moves through living things, just like it moves between potential and kinetic forms.
• Energy Conversion: Transformations Between Forms You will go deeper into how energy changes from one form to another, building directly on what you learn here.
• Phase Changes: Temperature Effects on State You will discover how energy causes matter to change state, connecting to stored and released energy.
• Particle Theory: Arrangement and Movement of Particles You will explore how the movement of tiny particles relates to kinetic energy at the smallest scale.

After mastering potential and kinetic energy, you will be ready for these next topics:

• Types of Energy: Mechanical, Electrical, Chemical You will expand your understanding to more forms of energy.
• Energy Conversion: Transformation Between Forms You will study energy transformations in greater detail.
• Efficiency: Energy Loss in Systems You will learn why not all energy converts perfectly from one form to another.
• Work and Time: Relationship Between Power and Energy You will connect energy to the concept of power.
• Force Applications: Real-World Applications You will apply what you know about forces and energy to real situations.
• Force Measurement: Quantifying Forces You will learn how to measure the forces that cause energy changes.
• Mechanical Advantage: Work and Force Relationships You will explore how machines use energy efficiently.