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Work

Work. Yes, yes, I know - work is where you go to get paid. Physics views it differently. Work – the energy transferred to an object when a force acting on the object moves it through a distance. WORK.

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Work

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  1. Work • Yes, yes, I know - work is where you go to get paid. • Physics views it differently.

  2. Work – the energy transferred to an object when a force acting on the object moves it through a distance.

  3. WORK Quantitatively: The work W done by a constant force on an object is the product of the force along the direction of displacement and the magnitude of displacement. W=(Fcos)x Units: =Nm=J=kg m²/s² Θ is the angle between the force & the displacement

  4. Work is a scalar quantity. Energy is defined as the ability to do work and therefore is a scalar quantity as well.It has no direction.

  5. Challenge Question: Two people exert a 10 Newton force on a block for 2 meters.  One person exerts her force at a 50-degree angle. Did both people do the same work???

  6. Person 2 does more workAll of her force goes to moving the block

  7. Consider this… I need a volunteer

  8. Is this person doing any work?

  9. Whenever the magnitude of the displacement (∆d) is 0, the work, W=(F cos θ) ∆d, is also 0.

  10. Another example to consider… • In the work equation, the angle θbetween the force and the displacement; when the force & the displacement are perpendicular, cos 90 is 0. Therefore, no work is done by the force on the object, even if the object moves and no energy is transferred to the object. • Give me an example…

  11. How many of you agree that work is always positive?

  12. Can work be negative?

  13. Negative work is done on an object when it is slowed by a force. Positive work is done when an object is sped up by a force.

  14. An example Fn Fn T =45o T fk x Fg Fg The work done by the person on the suitcase: W= The work done by Fg on the suitcase: W= The work done by friction on the suitcase: W=

  15. The area under the F-d graph is = to the W done by an applied force

  16. The total work done on an object is the sum of all the work done by individual forces.

  17. Work in groups for these next 2 questions…

  18. Text Book Questions: pg.181 #1-7pg. 183 #1-7pg. 226 # 1-4, 9-11

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