2 The Big Idea Energy can change from one form to another without a net loss or gain.
3 Discussion What is energy? Pros and cons? How many different forms of energy can you think of?Take 1 minute with an elbow partner and write down as many things you know about energy
4 Energy may be the most familiar concept in science, yet it is one of the most difficult to define. Persons, places, and things have energy, but we observe only the effects of energy when something is happening.Only when energy is being transferred from one place to another or transformed from one form to another.
5 Work! work = net force X distance When you apply a force on an object and it moves, you’ve done work.
6 Units of Work Remember Work = Force x Distance. What are the units for work?Newton x meters1 Nm = 1 Joule (J)
7 PowerPower equals the amount of work done divided by the time interval during which the work is done.
8 Units for Power Remember Work is measured in Joules Power is measured inJoules per Second
9 Mechanical EnergyThe energy due to the position of something Or the movement of something.The two forms of mechanical energy are kinetic energy and potential energy.
10 Potential Energy 3 kinds Elastic Potential Energy Chemical Energy A stretched or compressed springA stretched rubber bandA bow in a bow and arrowChemical EnergyIs released when a chemical change takes place.Gravitational Potential EnergyEnergy of position in a gravitational field.
11 Gravitational Potential Energy Focus on this type of potential energy.gravitational potential energy= weight X heightOrPE=mgh
12 Kinetic Energy Energy of motion Or Kinetic energy = 1/2 mass X velocity squaredOr
13 Total Mechanical Energy the total Mechanical energyAdd the Kinetic and potential energyME = KE + PELet’s think about the units.
14 Try it. An object has a mass of 10kg. It is 5m off the ground. It is moving 2m/sec.Find its gravitational potential energy.Find its kinetic energyFind its total mechanical energy
15 Simple MachinesA machine transfers energy from one place to another or transforms it from one form to another.A lever is a simple machine made of a bar that turns about a fixed point.The fulcrum is the fixed point that a lever operates on.
16 Mechanical Advantage. work input = work output The ratio of output forceto input force for a machineis called themechanical advantage.