330:148 (G) Machine Design 2. Force, Work and Power Weight, Force And
2. Force, Work and Power 330:148 (g) Objectives • Understand the difference between force, work, and power. Machine Design • Recognize and be able to convert between mass and weight. • Convert between English and metric units for force, work, and power. Nageswara Rao Posinasetti • Understand the basic principles of fluid mechanics as they apply to hydraulic and air cylinders or similar products. • Look up and/or calculate moments of inertia and section modulus for different shape parts. • Apply the principles of work, force, and power to moving machines. August 15, 2007 1 August 15, 2007 2 Weight, Force and Mass Work and Power Weight, W = m g Work = Force × Distance ft-lb or N m W = weight, lb or N Work done, W = F d M = Mass, lb or kg Power is rate of doing work W g = acceleration due to gravity, Power, P = 2 2 t 32.2 ft/s , 9.81 m/s t = time Force, F = m a a = acceleration August 15, 2007 3 August 15, 2007 4 Power and Speed Power and Speed 1 hp = 550 ft-lb/s P = T ω = 6600 in-lb/s P = Power, ft-lb/s or W T = Torque, ft-lb or N m = 33,000 ft-lb/min ω = Rotational speed in radians/second = 396,000 in-lb/min P T = Power in SI Units is Watts ω 1 hp = 746 W = 0.746 kW ω = 2 π n 60 n = revolutions per minute August 15, 2007 5 August 15, 2007 6 1 Torque Torque is a twisting moment Calculate the amount of torque in a shaft Rotates a part in relation to other transmitting 750 W of power while rotating T = F d at 183 rad/s.
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