EnergyEnergy

Review of Chapter 4Review of Chapter 4

EnergyEnergy

Energy can neither be created or destroyedEnergy can neither be created or destroyed Law of Conservation of EnergyLaw of Conservation of Energy We can only change it from one form into anotherWe can only change it from one form into another

Energy is classified in two categories (forms)Energy is classified in two categories (forms)

KineticKinetic The energy of motionThe energy of motion

PotentialPotential Energy that is storedEnergy that is stored

EnergyEnergy

KineticKinetic

How much kinetic energy an object has How much kinetic energy an object has depends on how much mass it has and depends on how much mass it has and how fast it is movinghow fast it is moving

Energy is related to mass and velocity by Energy is related to mass and velocity by the following equation:the following equation:

oKe=1/2•m•vKe=1/2•m•v22 The unit for Kinetic energy is the Joule.The unit for Kinetic energy is the Joule.

EnergyEnergy

PotentialPotential Potential energy can be classified into four Potential energy can be classified into four

categoriescategoriesChemical PotentialChemical Potential

Energy stored in chemical bondsEnergy stored in chemical bonds

Elastic PotentialElastic Potential Energy that is stored in things that stretch, twist or compressEnergy that is stored in things that stretch, twist or compress

Gravitational Potential EnergyGravitational Potential Energy Energy that is stored due to its position above the earthEnergy that is stored due to its position above the earth

PotentialPotential Stored energy due to positionStored energy due to position

EnergyEnergy

Chemical Potential EnergyChemical Potential Energy We change the energy stored in the chemical We change the energy stored in the chemical

bonds of gasoline into the kinetic energy of a bonds of gasoline into the kinetic energy of a car in motion.car in motion.

We change the chemical energy stored in a We change the chemical energy stored in a battery into the kinetic energy of a spinning battery into the kinetic energy of a spinning motor that runs a personal fan.motor that runs a personal fan.

EnergyEnergy

Elastic Potential EnergyElastic Potential Energy We store energy in a watch spring by We store energy in a watch spring by

compressing it ( winding) that changes into compressing it ( winding) that changes into kinetic as the spring unwinds. kinetic as the spring unwinds.

EnergyEnergy

Gravitational Potential EnergyGravitational Potential Energy

We use gravitational potential energy in roller We use gravitational potential energy in roller coaster design. We pull the cart up to the highest coaster design. We pull the cart up to the highest point so it has maximum potential energy and point so it has maximum potential energy and change that energy into motion of the cart as goes change that energy into motion of the cart as goes along the track.along the track.

Gravitational Potential Energy is related to mass Gravitational Potential Energy is related to mass and height above the earth by the following and height above the earth by the following equation:equation:

o GGpepe= m• 9.8m/s= m• 9.8m/s22 • h • h

EnergyEnergy

WorkWork Energy working over a distance.Energy working over a distance. Something has to move in order for work to be doneSomething has to move in order for work to be done Work is related to Force and distance by the Work is related to Force and distance by the

following equation:following equation:

o W = F • dW = F • d W is in Joules = J = Kg mW is in Joules = J = Kg m22/s/s22

F is in Newtons = N = Kg m/sF is in Newtons = N = Kg m/s22

d is in Meters = md is in Meters = m

EnergyEnergy

PowerPower Amount of work done or the amount of Amount of work done or the amount of

energy transferred over time.energy transferred over time. Power is related to work or energy and time Power is related to work or energy and time

by the following equation:by the following equation:

o P = w / tP = w / t P is in Watts = W = j/sP is in Watts = W = j/s w is in joules = J = kg mw is in joules = J = kg m22/s/s22

t is in seconds = st is in seconds = s