Energy NotesEnergy Notes

EnergyEnergy

When you do work on an object When you do work on an object you must displace that object you must displace that object from its rest position.from its rest position.

In this case that object then has In this case that object then has the ability to do work on some the ability to do work on some other object (one way is for the other object (one way is for the original object to collide into it)original object to collide into it)

We call this ability to do work We call this ability to do work

ENERGYENERGY..

EnergyEnergy

EnergyEnergy can exist because of the can exist because of the object's motion (Kinetic Energy) object's motion (Kinetic Energy)

It can also exist because of its It can also exist because of its position (Potential Energy). position (Potential Energy).

Kinetic EnergyKinetic Energy

Kinetic Energy=.5 (mass)Kinetic Energy=.5 (mass)(velocity)(velocity)22

KE= .5mvKE= .5mv22

the units on this will be kg mthe units on this will be kg m22/s/s22 or or a Joule—J (Nm—newtons x meters)a Joule—J (Nm—newtons x meters)

Sample Problem p. 193Sample Problem p. 193

Potential EnergyPotential Energy

There are different types of There are different types of potential energy (chemical, potential energy (chemical, elastic, gravitational, & nuclear), elastic, gravitational, & nuclear), but all depend upon the position but all depend upon the position of the object.of the object.

Gravitational Potential Energy Gravitational Potential Energy (GPE) is the energy due to an (GPE) is the energy due to an object's position above the Earth.object's position above the Earth.

Gravitational Potential EnergyGravitational Potential Energy

G.P.E. = (mass) x (acceleration G.P.E. = (mass) x (acceleration of gravity) x (displacement of of gravity) x (displacement of the object to the earth)=m•g•hthe object to the earth)=m•g•h

The units on this would also be a The units on this would also be a Joule.Joule.

Sample Problem p. 191Sample Problem p. 191

Elastic Potential EnergyElastic Potential Energy

Elastic Potential energy is the energy Elastic Potential energy is the energy due to the stretching or compression due to the stretching or compression of an elastic material.of an elastic material.

E. P. E. = .5 x (elasticity constant) x E. P. E. = .5 x (elasticity constant) x (amount of displacement from (amount of displacement from equilibrium)equilibrium)22= .5 k = .5 k ΔΔxx22

The units for k (elasticity constant) The units for k (elasticity constant) are in N/mare in N/m

Non-mechanical EnergyNon-mechanical Energy If the energy is a macroscopic If the energy is a macroscopic

quantity it is considered to be quantity it is considered to be mechanical energy (most kinetic or mechanical energy (most kinetic or potential energy). potential energy).

If not, then it is considered non-If not, then it is considered non-mechanical.mechanical.

Heat, Sound, Light, and all other Heat, Sound, Light, and all other electromagnetic radiation are types electromagnetic radiation are types of non-mechanical energy. (and of non-mechanical energy. (and actually are kinetic)actually are kinetic)