Physical Science Chapter 3 Energy

The Nature of Energy Energy – the ability to do work or cause a change. Two main types of energy: Kinetic and Potential Kinetic Energy: the energy of motion Potential Energy: Energy stored for use at a later time

Forms of Kinetic Energy Mechanical Thermal Electrical Radiant / Electromagnetic Sound

GPE = mass x gravity x height Mechanical Energy Movement of an object or it’s parts (based on amount of PE) GPE = mass x gravity x height

Thermal Energy total energy of the particles (atoms and molecules) in an object TE Increases = particle speed up, temperature up, overall KE up

Electrical Energy Passing of electrons as a current Flow of electricity through a conductor

Radiant / Electromagnetic energy Travels on waves – NO matter needed to pass the energy light, infrared, ultraviolet, microwaves, x-rays, etc… Longer wavelength = low frequency & low energy (Red) Shorter wavelength = high frequency & high energy (Violet)

Sound Vibration of particles CANNOT move in empty space – NEED matter

Calculating Kinetic Energy NEED TO KNOW - mass and speed (velocity) Energy is transferred during work The more work one does on an object… The more energy one imparts on the object Kinetic energy = Mass x Velocity2 2 ***When mass is doubled; Kinetic Energy is doubled ***When velocity is doubled; Kinetic Energy is quadrupled!!

What’s the Kinetic Energy? What is the Kinetic Energy (in Joules) of an object with a mass of 10 kg and a velocity of 10 m/s? When mass is doubled; Kinetic Energy is doubled When velocity is doubled; Kinetic Energy is quadrupled!!

Practice Velocity = Speed (distance/time) Unit = m/s Mass = you know this Unit = g or kg Joules = Amount of Energy Unit = J (1kg, 1m, 1sec) Mounted TV falls to the floor – How much KE did it have? M = 20 kg V = 2m/s KE = ½ m x v2 2. Skateboarder travels down a ramp – How much KE does she have? M = 65 kg V = 35m/s

Forms of Potential Energy Gravitational GPE Chemical Elastic Nuclear Magnetism

Chemical Energy stored in chemical bonds Bonds break/combine = release of energy

Gravitational (GPE) Stored above the ground or work done to lift an object above the ground Higher Elevation = Higher GPE Greater Mass = Higher GPE m = mass g = gravity acceleration (10m/s2) h = height GPE = mgh GPE = mass x 10 m/s2 x height Increase mass or height = increase in GPE

Practice - (N) Newtons = Mass on Earth  Pull of Gravity (1 N = .25 lbs) Unit = N (h) Height = You Know This Unit = meters Rock sitting on a hill – What is GPE? m = 100 N g = 10 m/s2 h = 300 m GPE = mgh 2. TV mounted on wall – What is GPE? m = 196N g = 10 m/s2 h = 2.5 m

Magnetism Magnetic fields/force Attract/repel objects

Elastic Objects that can be stretched or compressed Energy stored in springs, bow and arrow, stretched elastic or rubber bands.

Nuclear Energy Stored in subatomic particles (neutrons of an atom) The fusion of hydrogen into helium fuels the power of the sun

LAW OF CONSERVATION OF ENERGY Closed System Not Created or Destroyed Only Changes Forms 100% in = 100% out Most energy is lost to friction or thermal energy PHET.COM

Energy Efficiency Unwanted Energy * useful energy is less than total * Thermal/heat, friction, sound What is Efficient??? * more useful energy – less unwanted

Needed Improvements

ENERGY CONVERSIONS Transformation Transfer Converts from one form to ANOTHER form Transfer Converts from one form to the SAME form

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