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Work and Power

Work and Power. Work. Every day we do work. Many days we also don’t do work. Work is defined as a the product of force and the distance the object moves. Work = Force × Distance If the object does not move, work is not being done. Pushing the wall vs. writing with a pencil. Calculating Work.

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Work and Power

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  1. Work and Power

  2. Work • Every day we do work. Many days we also don’t do work. • Work is defined as a the product of force and the distance the object moves. Work = Force × Distance • If the object does not move, work is not being done. • Pushing the wall vs. writing with a pencil.

  3. Calculating Work • Force is measured in ______________. • Force can be calculated by taking the _______ and multiplying it by the _______ according to Newton’s _____ Law. • Distance will be measured in meters. • The unit of work then is a N•m a.k.a., the joule(J) – rhymes with cool.

  4. Example problems How much work is done when a 1N force moves a book 2m? Work = Force = W = F × d Distance =

  5. When 70.0 J of work is done to push a cart 3.5 m, how much force is used? Work = Force = W = F × d Distance =

  6. Haw far does a barbell move when the person expends 1100J in exerting 500N of force? Work = Force = W = F × d Distance =

  7. Power • How powerful a person is physically depends on two things: the amount of work they can do, and how fast they can do it. • Power is defined as a the amount of work done during a certain period of time. Power = Work ÷ Time • Who has more power a small person running fast or a big person walking slow?

  8. Calculating Power • Work is measured in ______________. • Work can be calculated by taking the _______ and multiplying it by the _______. • Time will be measured in seconds. • The unit of power then is a J/s, a.k.a. the watt (yes, like the unit on your power bill) whose symbol is W.

  9. Example problems How much power is required to do 55 joules of work in 55 seconds? Power= Work = Time =

  10. If it take 400 watts of power to push a heavy box a certain distance in 10 seconds, how much work was done? Power= Work = Time =

  11. How much time would it take to move a car 350 m if a 35 N force was pushing so that 2042 watts of power were used? Power= Work = Time =

  12. Example problems How much power does a person have if they push a cart 3.5m with 20N of force for 0.5 seconds? Power= Work = Time =

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