EF CH 13: Energy and Power01

We need energy to

• build shelters and other structures

• make products

• process and cultivate food

• heat or cool buildings and other things

• move or lift objects

-Tesla didn't deliver

Energy is the ability to do work.

• available in various forms:

  • kinetic

  • potential

  • elastic

  • thermal

Energy of motion

Kinetic Energy = 1/2 mass x velocity ²

Mechanical work performed on an object changes its kinetic energy.

​Work = 1/2 mass x velocity² - 1/2 mass x velocity²

^{at the end initially}

Energy of position, work required

to lift an object, it's the energy to overcome gravity

change in potential energy = mass x gravity x change in height

• When a spring is stretched or compressed from its unstretched position, elastic energy is stored in the spring

• Energy will be released when the spring is allowed to return to its unstretched position

• Elastic energy =

  1/2 spring constant x distance stretched²

the spring constant for a specific spring is based

on a comparison of how force causes the

spring to move, or how stiff it is

• is transferred whenever there exists a temperature difference within an object, between two bodies, or between a body and its surroundings

• heat flows from high to low temperature

Three modes of heat transfer

• Conduction

• Convection

• Radiation