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Work and Power Notes

This guide explains the fundamental concepts of work and power in physics. Work is defined as the product of force applied to an object and the distance over which that force is applied. It explores various activities that involve work and introduces the Work Triangle formulas. The concept of power, the rate at which work is performed, is also covered with relevant formulas, and introduces key units like watts and horsepower. Understanding these principles is essential for applications in everyday mechanics, engineering, and physics.

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Work and Power Notes

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  1. Workand Power Notes

  2. What is work ? • The product of the force applied to an object and the distance through which that force is applied.

  3. Mowing the lawn Weight-lifting Moving furniture up a flight of stairs Pushing against a locked door Swinging a golf club YES YES YES NO YES Is work being done or not?

  4. Calculating Work work = force x distance • All or part of the force must act in the direction of the movement.

  5. Work Triangle Formulas • W=? • W=F x d • F=? • F = W / d • d=? • d = W / F

  6. Do you do more work when you finish a job quickly? • Work does NOT involve time, only force and distance. • No work is done when you stand in place holding an object. • Labeling work: w = F x d • Newton X meter (N m) • Which also = (kg x m2) s2

  7. The Joule • 1 newton-meter is a quantity known as a joule (J). • Named after British physicist James Prescott Joule.

  8. Power • How quickly work is done. • Amount of work done per unit time. • If two people mow two lawns of equal size and one does the job in half the time, who did more work? • Same work. Different power exerted. • POWER = WORK / TIME

  9. Power Triangle Formulas • P=? • P = W / T • W=? • W = P x T • T=? • T = W / P

  10. The watt • A unit named after Scottish inventor James Watt. • Invented the steam engine. • P = W/t • Joules/second • 1 watt = 1 J/s

  11. watts • Used to measure power of light bulbs and small appliances • An electric bill is measured in kW/hrs. • 1 kilowatt = 1000 W

  12. Horsepower (hp) = 745.5 watts • Traditionally associated with engines. (car,motorcycle,lawn-mower) • The term horsepower was developed to quantify power. A strong horse could move a 750 N object one meter in one second. 750 N

  13. related to Work Power Defined as “Rate at which work gets done” Defined as “Applying a force a given distance“ Equation Power = Work / Time Equation Work = Force x Distance In other words Power = (F x D) ÷ time Short Name “JOULE” Newton Meter which is a Kgm2/s2 Units are Joules per second  “Watts” US units  Horsepower 1HP = 746 Watts

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