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Work and Power

Work and Power. Pioneer High School. Work. Work is done on an object when the object feels a net force, F, over a displacement, d. Force. displacement. Work. The formula to calculate work is: W = F ·d Work is measured in Joules, J. Sample problem.

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Work and Power

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  1. Work and Power Pioneer High School

  2. Work • Work is done on an object when the object feels a net force, F, over a displacement, d. Force displacement

  3. Work • The formula to calculate work is: • W = F·d • Work is measured in Joules, J

  4. Sample problem • A boat is tugged through the harbor with a total force of 5000N. How much work is done on the boat if it moves 2500m through the harbor?

  5. Work done lifting • Since the force of gravity is Fg = mg • Work = Fd • Work = mgd • W = mgd formula for lifting work

  6. Mr. Gonzalez, daunted by his ever graying hair, is having a midlife crisis and decides to start lifting weights. If Mr.G lifts 10.0kg of mass, to a height of 1.4m, how much work did Mr. G do?

  7. Work done to speed something up • Work done to accelerate something • Net Force causes acceleration, SF = ma • Work = net force ·displacement • W= SF · d • W = mad • Get it? Work makes you mad!

  8. A 2000kg drag racer accelerates at 15.0m/s2 over the 100.0m track. How much work is done on the dragster?

  9. Work done at an angle • Work can be done when the force and displacement are at angles to each other • W = Fdcosq F q

  10. A dock worker slides a crate along the ground holding a rope at an angle of 37o to the ground. If he pulls with a force of 500N over a distance of 2.0m, how much work did she do?

  11. Power • Power is the rate at which work is done • Power = work done the time it took • P = W t • Power is measured in watts, W • 1kilowatt, kW = 1000watts • 1 horsepower, hp = 746watts

  12. A wrestler is running up the stairs of the stadium to train for a match. If he is doing 50,250J of work to get to the top in 15.0s, how much power is he putting out?

  13. Power and velocity • Power can be calculated using force and velocity • P = W t • P = F·d t • P = F d t P = F·v

  14. A .001kg burst of methane is trapped in the duodenum of a customer at the Pioneer Cafetorium after eating a beef chimichanga. If the methane gas leaves at a velocity of 12.0m/s with a force of 25N, what is the customer’s intestinal power?

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