Energy Chapter 5
Dec 17, 2015
What is Work?
Work occurs when a force acts upon an object in the direction of the force applied
If you push against a wall and the wall doesn’t move, have you done any work?
Unit is the Joule (J)
What is Energy?
The ability to do work Unit is the Joule (J) Energy can be transferred from one object to
another
Kinetic Energy Energy of motion Kinetic Energy depends on speed and mass Kinetic energy = mv2
2 m is mass, v is speed (velocity) Speed has more of an effect on kinetic
energy than mass does because speed is squared.
Reflect
Draw a picture of something that has kinetic energy
Do the math:A 200 kg car is travelling at a speed of 10
km/hr. What is the kinetic energy of the car? Show all work
Potential Energy
Energy of position or shape
Ex.- the bow is not moving, but it has potential energy because work was done to change its shape
Gravitational potential energy
Energy due to an object’s position above the earth’s surface
The amount of energy is determined by the object’s weight and its distance above the earth’s surface
Gravitational potential energy = weight x height
Reflect
Draw a picture of something that has gravitational potential energy
Do the math:A toy is 40N and is on a shelf that is 10 meters
above the floor. What is the gravitational potential energy of the toy?
Show all work
Mechanical Energy
Total energy of motion and position of an object
Mechanical energy = potential energy + kinetic energy
Reflect
Do the math:A ball has a potential energy of 5 joules at the
highest point of a bounce and a kinetic energy of 25 joules while the ball is moving. What is the total mechanical energy of the ball?
Show all work
All forms of energy can be categorized as either kinetic or potential
PotentialStored energyEnergy of positionChemicalNuclearStored MechanicalSound
Kinetic Energy of motion Waves, electrons,
atoms, molecules, and substances
Radiant Thermal Motion Sound Electrical
Matter
All matter is made up of particles in motion. Because the particles are in motion, they have kinetic
energy. At higher temperatures particles move faster and
therefore have more kinetic energy.
Reflect Draw pictures of the molecules in ice,
water and steam in the boxes and answer the questions
Which has the most energy – ice, water, or stream?
Which has the least energy – ice, water, or steam?
Thermal Energy The total internal energy of the particles that make up an object. The vibration and
movement of atoms and molecules within the substance. The faster the particles move, the more thermal energy they have The bigger the object is, the more thermal energy it has because there are more
molecules that move Geothermal energy is an example of thermal energy
Reflect
Name 3 things that have a little bit of thermal energy
Name 3 things that have a lot of thermal energy
Which has more thermal energy – the ocean or a lit match?
Chemical Energy
Energy of a compound that changes as the atoms are rearranged
Form of potential energy The more atoms that are bonded together in a
compound, the more potential energy that compound has
Energy stored in the bonds of atoms: Biomass, petroleum, natural gas, propane and coal are
examples Food also has chemical energy
Photosynthesis uses light energy to make sugars
Plants absorb the light in their leaves and change it to chemical energy
When we eat, we absorb the chemical energy
Electrical Energy The energy of moving electrons Lightning and electricity Electricity is by the changing position of
magnets so it can be considered a form of potential energy
When you plug something in electrons move back and forth transferring energy so it is a form of kinetic energy
Electrical energy is produced at power plants and then transferred to your home
Sound Energy
Caused by an object’s vibrations Sound is the movement of energy through
substances in longitudinal waves Is both potential and kinetic To make an object vibrate, work must be done You change the shape therefore you create
potential energy When released, air particles are moved creating
kinetic energy
Light (Radiant) Energy
Radiant energy is electromagnetic energy that travels in transverse waves Light energy is an example of radiant energy Light energy is made up of photons which are little packets of energy Part of the electromagnetic spectrum
Electromagnetic Waves have different wavelengths
When you listen to the radio, watch TV, or cook dinner in a microwave oven, you are using electromagnetic waves.
Source: http://imagers.gsfc.nasa.gov/ems/waves3.html
Radio waves, television waves, and microwaves are all types of electromagnetic waves. They only differ from each other in wavelength. Wavelength is the distance between one wave crest to the next.
Source: http://imagers.gsfc.nasa.gov/ems/waves3.html
Waves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom.
Reflect
Put the following in order of wavelength starting with the shortest and ending with the longest: Infrared; TV; X-rays; AM Radio; Visible light; Microwave
Nuclear Energy
The energy within the nucleus of an atom Two types:
Fusion – this is done by the sun. It is when the nuclei of atoms are fused together thereby releasing a huge amount of energy
Fission – this is done by nuclear power plants. It is when the nuclei of an atom is broken apart thereby releasing a huge amount of energy