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Chapter 2 - Work

What's Ahead. Mechanical WorkForceTorqueFluid WorkPressureElectricalVoltage. Why is Work Important in Technology?. Useful Work may come in various formsMoving a steel beamturning the crankshaft in a carheart pumping blood through your bodyWork causes a specific change. What's The Technical

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Chapter 2 - Work

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    1. Chapter 2 - Work Overview

    2. Whats Ahead Mechanical Work Force Torque Fluid Work Pressure Electrical Voltage

    3. Why is Work Important in Technology? Useful Work may come in various forms Moving a steel beam turning the crankshaft in a car heart pumping blood through your body Work causes a specific change

    4. Whats The Technical Definition of Work in Mechanical Systems? Two factors of Work An applied Force A distance through which the object moves while the force is being applied Equation Work = Force x distance Mechanical/Linear

    5. Whats The Technical Definition of Work in Mechanical Systems? Also is true for Rotational movement Work = Torque x Angle through which the object turns Mechanical/Rotational

    6. Concept of Work in other Energy Systems Fluid System Fluid Work = Pressure Difference x Volume Electrical System Electrical Work = Voltage x Charge

    7. Unifying Concept Unifying means that one simple concept can be applied to all of the systems. Unit 1 Force was a unifying concept...There was a quantity in each system that caused movement (prime mover) Unit 2 Work is also a unifying concept.

    8. Unifying Concept Mechanical Work = Force x Distance Mechanical Work = Torque x Angle Fluid Work = Pressure x Volume Electrical Work = Voltage x Charge

    9. Unifying Concept All Four fit the following format Work =(Force or Forcelike Quantity) x (Distance or Quantity moves) We can make all four specifically fit into this concept!

    10. Work in Mechanical Systems Chapter 2 Section 1

    11. Work Done by a Force Mechanical work is when a force moves an object. Equation Work = Force x Distance W = FxD Units English Ftlb SI Nm

    12. Work Done by a Force Example A weightlifter raises a 200lb barbell 5ft. What is the amount of work done in lifting the barbell?

    13. Work Done by a Force Other Unit Joule = 1 Nm They are the same The distance is ONLY the used while the force is being applied

    14. The Effect of Doing Work Changes Position Vertically (Changes Potential Energy) Horizontally Changes Speed Kinetic Energy Or Both

    15. Efficiency Rating of machines Compares Output and Input Output work done by machine Input work done to the machine

    16. Efficiency Equation Efficiency = workout/workinput x 100% Eff = WO/WI x 100% Measured in % Never over 100% Smaller number always on top

    17. Efficiency A block and tackle is used to lift an engine. The engine weighs 600lb and is raised 0.9 ft. The operator pulls with a force of 100lb over 6 ft. What is the Input work, output work, and efficiency.

    18. Machines Purpose: To make work easier Less force Not less work. Actually more work. Examples of Simple Machines Inclined Plane Pulley Wheel and Axle Lever

    19. Radians 1 radian the angle that is made when the distance measured along the arc is equal to the radius of the circle.

    20. Radians Conversions 2? = 1 rev = 360o (2? = 6.28 rad) 45o = ?/4 = .785 rad 90o = ?/2 = 1.57 rad 180o = ? = 3.14 57.3 = 1 rad

    21. Rotational Work When a torque causes motion Equation Work = Torque x Angle W = T x ? Same units as Linear work.

    22. Rotational Work Example A simple mechanical winch has a crank handle of one foot. A force of 20 lb is required to turn the crank. How much work is done turning the crank through five revolutions?

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