The Nature of Energy

What is Energy?

Energy – the ability to do work or cause

change.

when an object does work on another object, some

of the energy is transferred to that object.

Energy is measured in Joules

Joule – a unit of measure equal to one newton-meter

What is work?

Work – force exerted on an object that causes it

to move

Example: pushing a shopping cart

Two Types of Energy

Kinetic Energy – energy in motion

Potential Energy – stored energy

Kinetic Energy

The more work you do on an object, the more energy you give the object.

The greater the mass of a moving object, the more kinetic energy it has. (Ex. a bowling ball has more kinetic energy than a golf ball traveling at the same velocity)

Kinetic energy increases as velocity increases.

Calculating Kinetic Energy

Kinetic Energy = Mass x Velocity2

2

Ex. – What is the kinetic energy of a 10kg wagon

moving at 5 m/s?

kinetic energy = 10 x 52 = 10 x 25 = 250

2 2 2

kinetic energy = 125 Joules

Potential Energy

Energy that is held in readiness and therefore

has potential to do work.

Ex. A spring compressed in a wind-up toy

Elastic potential energy – energy stored in a

stretched or compressed object (rubber band)

Potential Energy

Gravitational potential energy (GPE)–

potential energy that depends on height; an

object lifted.

Gravitational potential energy = weight x height

Ex. What is the GPE of a rock that weighs 600 newtons

positioned 20 meters of the ground?

GPE = 600 x 20

GPE = 12,000 Joules