Energy and Stored Energy Essay

Submitted By 1009080chen
Words: 982
Pages: 4


Welcome to SCIE 150:
The Science of Everything


Last Class


Today: Energy (Chapter 2)
• Contrast the general properties of the different forms of energy.

• Articulate the difference and relation between
Energy, Power and Work.
• Compare the concepts of Temperature with Heat.
• Examine the implications of the laws of
Thermodynamics in our lives.

• Explore possible sources of energy for our society.


• Doing anything requires energy
• Everyday life “energy” = exuberance
• Physics takes it more seriously: the capacity to do work

• What types of energy can you think of offhand?


Two major types: potential, kinetic

Stored energy

Energy of something in motion, something happening


Laws of Thermodynamics
• 1st: Energy is conserved
• 2nd: Energy always goes from more useful to less useful forms
▫ There’s no such thing as a free lunch
▫ Everything is taxed...

• 3rd: disorder (entropy) increases


Energy – a conserved quantity
• Energy is conserved. What does this mean?

• Can’t be created or destroyed
▫ I can’t suddenly blast off into space
▫ I can’t easily stop a speeding car

• But it can be converted from one form to another
▫ I can eat a chocolate bar, and literally get more energy for running
▫ I can shine a light on a solar panel, and get electrical power for a device


Transferring Energy


Doing work = the transfer of energy
• You have some money (energy), and in order to do something with it, you have to spend it (do work) 10

Doing Work
• Doing work = transferring energy
• Energy = capacity to do work
• Basic work: force applied through a distance
• The unit of energy (and work): the joule (J)

1 J: lifting a litre bottle of water 10cm
1 slice of cherry pie = 2,000,000 J
Bicycling or rowing: 1,000 J per second
Flashlight battery stores 10,000 J


• Power = Energy/time
▫ Watts = Joules/s
▫ A rate of energy flow

• Which uses more power? A:
• Which uses more energy? • Which do you think you get B: billed for?


Kinetic Energy
• Energy of motion
• What factors determine it?

• Getting rid of it isn’t easy... 13

Radiative Energy

• What type of light carries the most energy?
• A) Radio B) Visible C) Ultraviolet D) Gamma rays


Sound Energy


What makes this dangerous?


Potential Energy

• Elastic, chemical, electrical, gravitational


Another Potential Energy
• Fat Man and Little Boy
▫ The bombs dropped over Nagasaki and

• Do they have potential energy? • What kind?


Energy = mass x (speed of light)2

• 1-megaton H-bomb converts mass of a quarter of a can of soda into energy
• The Sun turns some of its mass into energy
• The Big Bang turned a whole lot of energy into the mass of the universe


Storing Energy
• We live in an electric world
• How do we store electrical energy that we’ve produced? 20

Gravitational Potential Energy and Kinetic Energy


I dare you to physics

Hold a bowling ball to your nose
Release it

• Energies involved? Energy loss?

Should you move your face? 22

Back and Forth


Energy Loss?
• 2nd: Energy always goes from more useful to less useful forms
▫ There’s no such thing as a free lunch
▫ Everything is taxed...

• Object pushed on a carpet slides to a stop, what happens to its kinetic energy?
A. It disappears
B. It is turned into heat via friction
C. It is unchanged
D. It is stored as potential energy


Friction to Heat

• Friction does work, transferring the energy from
“useful” kinetic to “waste” heat


Kinetic Energy and Temperature
• Particles (atoms and molecules) of any material/object always moving…
• Temperature is average kinetic energy of particles.


Temperature Scales


Heat Flows
• Heat always flows from…