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Energy, Friction & Efficiency

Energy, Friction & Efficiency. Energy = the ability to do work When work is done, energy is used Work is the transfer of energy. The Law of Conservation of Energy. Energy can’t be created or destroyed, it has to come from somewhere What are some sources of energy?.

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Energy, Friction & Efficiency

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  1. Energy, Friction & Efficiency

  2. Energy= the ability to do work • When work is done, energy is used • Work is the transfer of energy

  3. The Law of Conservation of Energy • Energy can’t be created or destroyed, it has to come from somewhere • What are some sources of energy?

  4. Which form of energy powers most of our machines? • Thermal (heat) • Electrical • Mechanical (our muscles) • Chemical (gas) • Sound • Elastic • Magnetic • Nuclear • Solar

  5. When something is moving it has Kinetic Energy • Potential Energy is stored energy due to position or condition • Chemical potential energy: a battery, food, fuel • Electrical potential energy: a battery • Gravitational Potential Energy: a skier on top of hill, a rock on top of hill, water in a dam (hydro electrical)

  6. For Example • A backhoe lifts the dirt out of a hole • Work: moving the dirt upward against the force of gravity uses: • chemical energy (fuel) • kinetic energy (shovel) • What kind of energy does the dirt have once it is in the air?

  7. Transmission • Energy can be converted from one form to anther or it can be transmitted • Transmission: energy is transferred from one place to another but no energy is changed or converted Ex. bike: energy from one sprocket to another Ex. electrical wires: from generating station to house

  8. Friction • Friction is the resistance of motion when the surfaces of two objects comeinto contact • Friction opposes motion so you will never get the same amount of work out of a machine as the effort put in it • The lost work appears as heat or sound

  9. Many machines require very little friction and need to be lubricated with oil or grease Ex. rollerblades, pistons in a car • Some machines depend on friction to work properly Ex. erasers, car brakes, parachutes

  10. Efficiency • Efficiency is a comparison of the useful work provided by a machine to the work supplied to the machine • The higher the efficiency, the better the machine is at transferring energy Efficiency = work done by a lever on a load x 100% work done on a lever by effort force

  11. Work done on a machine = work done by the machine + energy lost to friction

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