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Work, Energy and POWER!!!

Work, Energy and POWER!!!. Section 11.1 BC Science Probe 9. What is Work?. In science, work is defined as the transforming or converting of energy .

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Work, Energy and POWER!!!

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  1. Work, Energy and POWER!!! Section 11.1 BC Science Probe 9

  2. What is Work? • In science, work is defined as the transforming or converting of energy. • So every time that you flip a switch, or plug something in, work is done! (Do NOT use this as an excuse to say that you have done your WORK at home!!!)

  3. What is Work? • Because work is a change in energy, it gets the same units as energy: Joules (J) • What are some examples of work being done?

  4. What is Work? • Because work is a change in energy, it gets the same units as energy: Joules (J) • What are some examples of work being done? • A battery in a flashlight producing an electric current to produce light energy from electrical energy • A motor where electrical energy is converted into motion

  5. What is Energy? • In general, we can say that an object has energy (E) if it has the ability to do work. • There are lots of kinds of energy. Here are some examples…

  6. What is Energy? • We can classify all of these kinds of energy into two major types: • Potential energy (PE): energy that can be stored in an object • Kinetic energy (KE): energy that an object has because of its motion

  7. What is Energy? • The different kinds of energy can be converted into each other. • For example: • If you throw a ball in the air, you give it kinetic energy. • This is converted to gravitational potential energy as the ball rises (because it has the ability to fall) • At its highest point, all of the ball’s kinetic energy has been converted to gravitational potential energy • As it falls, the GPE gets converted back to kinetic energy! • WORK has been done!

  8. What is Energy? • Kinetic energy (KE) depends on the mass and speed of an object. • The greater the mass or speed, the greater the KE of the object. • When an object’s speed changes, work is done that equals that object’s change in KE.

  9. What is Energy? • Here’s an equation to show it: • W = work • KEfinal= final kinetic energy • KEinitial= initial kinetic energy W = KEfinal – KEinitial

  10. What is Energy? • We can even shorten the equation: W = ΔKE • Remember that Δ is delta and it shows a change • So work equals the change in kinetic energy!

  11. What is Energy? • Since our original definition of work was something like a change into another type of energy, we can shorten the equation one more time  W = ΔE

  12. What is Energy? • All of the types of energy that we have talked about can be converted from one type of energy into another. • When this happens, there is no overall loss in energy because as one type decreases, another will increase by the same amount.

  13. What is Energy? • This gives us the Law of Conservation of Energy: • In any closed system, the total amount of energy (including potential energy) remains constant • This means that when you add the amounts of all the different kinds, the total amount of energy will never change.

  14. What is POWER? • Power (P) is the rate at which energy is transformed, or the rate at which work is done. • If you walk or run up a hill, you do the same amount of work, but to run up the hill in a short amount of time, you need more power than when you walk up slowly.

  15. What is POWER? • Power is measured in watts (W) • One watt is equal to one joule per second (1W = 1J/s)

  16. What is POWER? • This is how we can calculate power: P = ΔE/Δt • P = power • ΔE = the amount of energy transformed (in joules) • Δt = the time interval (in seconds)

  17. What is POWER? • Since we know that W = ΔE, we can substitute W for ΔE P = W/ Δt

  18. Assignment • CYU page 339 • # 1, 2, 3, 4, 7, 8, 9

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