IOT POLY ENGINEERING

1. IOTPOLYENGINEERING 3-9 UNIT 3 – ENERGYAND POWER UNIT 3 Topics Covered • Energy Sources – Fuels and Power Plants • Trigonometry and Vectors • Classical Mechanics: • Force, Work, Energy,and Power • Impacts of Current Generation and Use

2. WORK IOTPOLYENGINEERING 3-13 • The man below is holding 1 ton above his head. • Is he doing work? • No, the object is not moving. • Describe the work he did do: • Lifting the 1 ton from the ground to above his head.

3. WORK IOTPOLYENGINEERING 3-13 • Velocity, acceleration, force, etc. mean nearly the same thing in everyday life as they do in physics. • Work means something distinctly different. • Consider the following: • Hold a book at arm’s length for three minutes. • Your arm gets tired. • Did you do work? • No, you did no work whatsoever. • You exerted a force to support the book, but you did not move it. • A force does no work if the object doesn’t move

4. WORK IOTPOLYENGINEERING 3-13 • WORK = FORCE x DISTANCE • The work W done on an object by an agent exerting a constant force on the object is the product of the component of the force in the direction of the displacement and the magnitude of the displacement.

5. WORK IOTPOLYENGINEERING 3-13 • WORK = FORCE x DISTANCE • W = F x d • Consider the 1.3-lb ball below, sitting at rest. How much work is gravity doing on the ball?

6. WORK IOTPOLYENGINEERING 3-13 • WORK = FORCE x DISTANCE • W = F x d • Now consider the 1.3-lb ball below, falling 1,450 ft from the top of Sears Tower. How much work will have gravity done on the ball by the time it hits the ground? • F = 1.3 lbs W = F x d • d = 1,450 ft. = (1.3 lb) x (1,450 ft.) • W = ? W = 1,885 ft-lb

7. Work IOTPOLYENGINEERING 3-13 • You are pulling a wagon with a 20 lbs of force at a 60o angle. You pull the wagon 10 feet, how much work did you do? 20 lbs Fy 60o Fx

8. WORK IOTPOLYENGINEERING 3-13 • Units for Force • English System Metric • lbs Newton (N)=kg-m/s2 • Units for Work • English System Metric • ft-lbs Joule (J) = N*m

9. Efficiency IOTPOLYENGINEERING 3-13 • Efficiency compares how well you did to the best that you could have done. • A basketball player shoots 20 free throws and makes 15. What is his shooting percentage/efficiency? • Efficiency is always less than or equal to 100%

10. Efficiency IOTPOLYENGINEERING 3-13 • Units for Efficiency • No Units or percentage

11. Efficiency IOTPOLYENGINEERING 3-13 • You are pulling a wagon with a 20 lbs of force at a 60o angle. How efficiently are you using your pulling 20 lbs Fy 60o Fx

12. POWER IOTPOLYENGINEERING 3-13 • Power is the rate of doing Work • P = • The less time it takes…. • The more power • Units: • Watts, Horsepower, Ft-lbs/s • W t

13. POWER IOTPOLYENGINEERING 3-13 • Three Buddhist monks walk up stairs to a temple. • Each weighs 150 lbs and climbs height of 100’. • One climbs faster than the other two. • Who does more work? • They all do the same work: • W = F x d (force for all three is 150 lb) • = (150 lb)(100’) • W = 15,000 ft-lb • Who has greater power?

14. Work IOTPOLYENGINEERING 3-13 • You are pulling a wagon with a 20 lbs of force at a 60o angle. You pull the wagon 10 feet in 10 seconds, how much power did you use? 20 lbs Fy 60o Fx

15. Tomorrow IOTPOLYENGINEERING 3-13 WORKSHEET • Problem Solving Steps: • Write given, sketch and label a diagram • Write equation/formula • Substitute values and solve • Check answer • Box answer