Exploring Energy: Kinetic and Potential

Engineering Connection

A firm understanding of energy types and energy conversion is essential to understanding the different forms of energy (and energy transfers) so common in our everyday lives, as well as a basis for comprehending more advanced concepts in engineering, physics, renewable energy, electrical generation and other fields. It takes energy to power vehicles, but the same task may be performed by energy in different forms (gasoline, lithium-ion batteries, etc.), as designed by engineers to meet specific functional requirements.

Introduction/Motivation

In the previous lesson, we learned that energy is the ability to make things happen. Energy is in use everywhere and comes in many different forms. It can be stored and then employed to do things for us. In fact, all types of human activities require the input of energy. Gasoline is necessary to power automobiles, ships and airplanes so that we can travel long distances. Electricity powers light bulbs so we can continue to study, work and have fun after dark. Fireplaces, electrical heaters and gas furnaces provide warm indoor air so we can survive when the weather is freezing. And food, grown with the energy from the sun, is our fundamental source of energy to support our lives. Everywhere you look, in all sorts of different forms, energy is present and important in our daily lives.

Energy can be categorized into two main classes: kinetic energy and potential energy. Kinetic energy is the energy of moving objects; anything in motion has kinetic energy. It is calculated as KE = (1/2) x mass x speed2. The heavier an object, the more kinetic energy it has when in motion. If an object's mass is doubled, its kinetic energy under the same speed is also doubled. The faster an object moves, the more kinetic energy it has. If an object's speed is doubled, its kinetic energy is quadrupled.

Gravitational energy, chemical energy, elastic energy and heat/thermal energy are all categorized as stored energy—also called potential energy. Energy can be stored in chemicals (food, batteries), height (gravitational), elastic stretching, etc. Gravitational energy is the energy that is stored due to the height of objects. Gravity is the force that pulls things down to Earth. The higher an object, the more gravitational energy it has. Often, gravitational energy (a form of potential energy) is converted to kinetic energy, such as when objects drop off cliffs or roll down ramps. Chemical energy is the energy that is stored in the chemical bonds of molecules. This energy is released during chemical reactions. Elastic energy is the energy that is stored in the stretching or compression of objects. Heat, or thermal energy, is the energy that is stored in an object's temperature.

One of the most important concepts about energy is that energy can be neither created nor destroyed; it can only be transferred, or converted, from one form to another. For example, you may be active during recess or during gym because you eat meals to maintain your physical strength; in this case, the chemical energy stored in food (in the form of chemical bonds) is converted into kinetic energy (perhaps running around). Electrical energy is converted into light that we use to see in the classroom; it also powers the air conditioner or heater so we can study in a comfortable air temperature. Can you think of some more examples of energy conversion from one form to another?

Participation Grade:

• You are a superhero and have three superpowers.

• Write a paragraph explaining what your superpowers are, how you use them, and what kind of energy they use.

  • Kinetic energy

  • Potential energy

  • Gravitational energy

  • Energy Transfer

  • Chemical energy

  • Elastic energy

  • Thermal energy