Energy: Forms and Changes

Chapter 16

Energy:

• is the ability to do work

• is measured in joules (J)

Objects can gain energy when work is done on them

There are five different forms of energy

• Mechanical

• Heat

• Chemical

• Electromagnetic

• Nuclear

MechanicalEnergy of motion

Heat• Internal motion

of atoms

• The greater the motion, the more heat the object contains

Heat Energy

Chemical •Energy found in the bonds of atoms

•Released when those bonds are broken

Chemical Energy

Electromagnetic

Moving electrical charge

Electromagnetic Energy

NuclearNucleus in atom break apart (fission)

nuclei join (fusion)

or

Nuclear Energy

Energy can be classified as either kinetic or potential

• kinetic is the energy of movement

• potential is the energy of position or shape

• Energy of position or shape

• Energy is stored for later use

If potential energy depends upon height (gravity), then formula is:

GPE = weight X height(weight = mass X gravity constant)

If a 10 N rock is sitting on a wall 10 meters high, what is

its potential energy?

Kinetic Energy (KE) = mass X velocity2 2

Which affects KE the most – mass or velocity?

Kinetic or Potential Energy

Energy Conversions

•Like matter, energy is neither created nor destroyed by ordinary means; however, it can be changed from one form to another.•All forms of energy can be converted to other forms.

Potential to Kinetic Conversions

At this position, is there kinetic and/or potential energy?

How many different ways can the sun’s energy be converted?

How many different conversions of energy occur when one uses a hairdryer at home.

Energy Conversion

Einstein1905

Part of Einstein’s theory of relativity deals with the concept that mass and energy are directly related.

• He stated that mass and energy can be converted into each other. If matter is destroyed, it becomes energy and energy can become mass.

This is the theory of how the sun creates so much energy – some mass is destroyed causing much energy to be created.

E = mc2

How does energy relate to:• speed?

• more energy, more speed

• momentum?

• energy is transferred

• force?

• energy needed to change motion

• power?

• rate of energy consumed

• work?

• energy is conserved (input vs output)