Energy of Motion

1. Energy of Motion Source: www.teachengineering.org

2. Energy of Motion • What has more potential energy: a boulder on the ground or a feather 10 feet in the air?

3. Engineering Connection • Automobiles, appliances, computer hardware, factory equipment and roller coasters use mechanical motion. • Elevators, power plants and race cars, use work and power. • Dams generate electricity from the flow of water. • Protective "crumple zones" and safety devices in vehicles absorb energy being transferred during a crash. • Baseball and golf equipment has become safer and more efficient. • Vehicles have become more aerodynamic to become more efficient.

4. Kinetic and Potential Energy of Motion Mechanical engineers are concerned about the mechanics of energy — how it is generated, stored and moved. Product design engineers apply the principles of potential and kinetic energy when they design consumer products. For example, a pencil sharpener employs mechanical energy and electrical energy. When designing a roller coaster, mechanical and civil engineers ensure that there is sufficient potential energy (which is converted to kinetic energy) to move the cars through the entire roller coaster ride.

5. Kinetic and Potential Energy • Energy is the capacity for doing work. • Work is done when a force moves an object over a given distance. • The capacity for work, or energy, can come in many different forms. Examples of such forms are mechanical, electrical, chemical or nuclear energy. • Whenever something moves, you can see the change in energy of that system. Energy can make things move or cause a change in the position or state of an object.

6. Mechanical energy isthe form of energy that is easiest to observe on a daily basis. All moving objects have mechanical energy. There are two types of mechanical energy: potential energy and kinetic energy. Potential energy is the energy that an object has because of its position and is measured in Joules (J). Potential energy can also be thought of as stored energy. Kinetic energy is the energy an object has because of its motion and is also measured in Joules (J). Due to the principle of conservation of energy, energy can change its form (potential, kinetic, heat/thermal, electrical, light, sound, etc.) but it is never created or destroyed.

7. Potential Energy • Within the context of mechanical energy, potential energy is a result of an object's position, mass, and the acceleration of gravity. • A book resting on the edge of a table has potential energy; if you were to nudge it off the edge, the book would fall. • It is sometimes called gravitational potential energy (PE).

8. Potential Energy • PE = mass x g x height • PE = weight x height • PE is the potential energy • g is the acceleration due to gravity • At sea level, g = 9.81 meters/sec2 or 32.2 feet/sec2. • In the metric system, we would commonly use mass in kilograms or grams with the first equation. With English units it is common to use weight in pounds with the second equation.

9. Kinetic Energy • Kinetic energy (KE) is energy of motion. Any object that is moving has kinetic energy. An example is a baseball that has been thrown.

10. Kinetic Energy & Total Mechanical Energy • Here KE stands for kinetic energy. • Note that a change in the velocity will have a much greater effect on the amount of kinetic energy because that term is squared. • The total amount of mechanical energy in a system is the sum of both potential and kinetic energy, also measured in Joules (J). Total Mechanical Energy = Potential Energy + Kinetic Energy

11. Engineers must understand PE & KE • This can be done by raising the cars to a great height. • Then, the increased potential energy of the cars is converted into enough kinetic energy to keep them in motion for the length of the track while overcoming friction. • Roller Coaster Design involves both mechanical and civil engineers. • At the beginning of the roller coaster, the cars must have enough potential energy to power them for the rest of the ride.

12. Kinetic and Potential Energy • Energy: Energy is the capacity to do work. • Mechanical energy: Energy that is composed of both potential energy and kinetic energy. • Potential energy: The energy of position, or stored energy. • Kinetic energy: The energy of motion. • Conservation of energy: A principle stating that the total energy of an isolated system remains constant regardless of changes within the system. Energy can neither be created nor destroyed.

13. How can you throw a ball and have its energy change from kinetic to potential and back to kinetic without touching the ball once it releases from your hand?

14. Did you know that… there is another form of potential energy, not related to height, which is called spring potential or elastic potential energy?