Energy: Introduction

1. Energy can be said to be based on all of the following except: How far an object moves. How much force is applied to an object. How many seconds a force is applied for. How fast an object is moving.

Energy is based on motion. An object moving Active energy An object that has the potential to be moving Stored energy

Energy of Motion – Kinetic Energy Motion of objects larger than molecules Typically motion of objects we can see with the naked eye

Kinetic Energy Get used to the equation: 𝐾𝐸= 1 2 𝑚 𝑣 2

Potential for Motion – Gravitational Potential Kinetic Energy A macroscopic object could move faster because gravity is pulling on it.

Gravitational Potential Energy Get used to the equation: 𝐺𝑃𝐸=𝑚 𝑎 𝐺 ℎ

Potential for Motion – Elastic Potential Kinetic Energy An object could move faster because there is either attraction or repulsion acting on it.

Elastic Potential Energy Get used to the equation: 𝐸𝑃𝐸= 1 2 𝑘 𝑠 Where k is a “springiness” constant… more on that later.

How is energy given to an object? How do we get objects to move? Apply a force! If we apply a force but nothing moves, did we give it energy? Not only must a force be applied, but it must move the object. NO NO NO

Work Doing work to an object gives it energy. Work is defined in physics to be “effort” How measure “effort” 𝑊 = 𝐹 𝑑 Work equals the product of force applied and the distance over which it was applied.

How to show transfers of Energy LOL Diagrams How to show transfers of Energy

The LOL Original Objects Final go here Drawn as: Bar graph (for original case) Circle (for energy transfers) Bar graph (for final case) Describes energy transformations over a given time period, between objects. Objects go here Original Final

Ex: an object falls from up high. System: box and earth. A box falls from the side of a table. Original case: box on edge of table. Final case: box about to hit ground. Earth’s Gravity BOX

Acquire LOL Practice

What is it? How is it created? Thermal Energy What is it? How is it created?

Energy of Motion – Thermal Energy The average motion of all the particles in an object Particle means atoms and/or molecules and/or proton/neutrons in this case

Friction can generate T.E. Rub table until warm. Rub table until HOT. Difference? What’s happening at the atomic level?

Energy Leaving the System How to diagram it with an LOL.

Ex: Rubbing the table. System: your hand. You rub the table with your hand as hard as you can. Original case: rubbing begins. Final case: rubbing done, hand warm. HAND T.E. to table.

Acquire LOL Practice

Chemical and Light Energy Energy from Atoms

Potential – Chemical Energy Energy is trapped in the chemical bonds between atoms in a molecule. Most molecules, when given a little push to break apart, separate and move very quickly. What is that fast atomic motion known as?

Transfer of Energy – Light Energy Light is the succession of a magnetic field and electric field. Each one creates another field a little further out Known as electromagnetic radiation for a reason! Light comes from the motion of electrons, creating an electric field

Transfer of Energy – Light Energy cont. What was thermal energy again? Atoms moving around When an atom moves, so does its electrons Recall: moving electrons create light

Transfer of Energy – Light Energy cont. It is a transfer of energy because light is not made of matter Light is like potential energy because it can make things (like electrons) move Light is like kinetic energy because it itself, moves It’s moving potential energy… so it’s a bit of both

(4 min) To your partners: Where does light come from? What can it move? Why is it like both Kinetic and Potential Energy?