Elements of Power Types and Calculations

What is Work and Power? Work is the result of force displacing a mass Power is the rate at which work is done Typically mechanical, electrical, or fluid

Mechanical Calculations P = power measured as ft-lb/s W = work, measured as ft-lb t = time measured as s 1 hp = 550 ft-lb/s

Example If Jessica moves her 103 pound (lb) body up 6 feet (ft) of stairs in 2 seconds (s), how much work did she perform? How much power did she use?

Your Turn An escalator moves 60 people per minute from one floor of a mall to the second floor. The mall’s floors are 20 ft apart, and the average passenger weighs 150 lb. How much power does the escalator need?

Solution Available from Teacher

Electrical Work and Power Commonly measured as watt (W) Also measured as joule or horsepower

Electrical Calculations Electrical power is determined by the formula P = IV V = voltage measured as volt (V) P = power Measured as watt (W) and horsepower (hp) I = current measured as ampere (A) 1 hp = W 1 W = hp

Electrical Calculations A house is wired such that a typical circuit can allow 15 A. Which two appliances can be used simultaneously without blowing a circuit? Hair dryer (1600 W, 110 V) Microwave (500 W, 100 V) Toaster (450 W, 110 V) Coffee maker (200 W, 120 V) Dishwasher (1800 W, 120 V) Flat iron (72 W, 110 V)

Your Turn Assume that a shop is wired so that a typical circuit is 20 amps. Which appliances can be used simultaneously? A.Band saw (1 hp, 110 V motor) B.CNC laser (200 W, 120 V) C.Laser engraver (3500 W, 220 V) D.Light (each) (400 W, 120 V) E.Computer (250 W, 120 V) F.3D printer (1600 W, 220 V)

Power Calculations Using the previous problem, how much power will be generated if the force is applied at a rate of 200 rpm?

Your Turn A shaft has a force of 13.5 pounds applied 2 feet from the pivot point. What is the resulting torque? How much power is generated if the torque is produced at 3200 rpm?

Solution Available from Teacher

Fluid Power Operated by compressed fluid Low load-carrying capacity Requires mechanical stops if not used with servomotors

Fluid Calculations p = Pressure, measured in pounds per square inch (psi) F = Force, measured in pounds A = Area of the base of the fluid container FF A A piston has the geometric shape of a circle so how is area calculated? If the piston diameter is 4 in. then what is the area?

F = Force being applied A = Area to which force is being applied

Your Turn 50 pounds of force is applied to a 1 inch pneumatic cylinder. What pressure is created in the cylinder?

Solution Available from Teacher

Your Turn A hydraulic pressure of 150 psi is applied to a piston that has a 4 inch diameter and 9 inch stroke. What is the power produced by the piston that moves its full stroke in 2.5 s?

Solution Available from Teacher

Torque Torque, , is a twisting force on a shaft Torque measured as in.-lb or ft-lb  = dFsinθ A force applied at 90 degrees allows the formula to be simplified to  = dF  = 90  r F

Finding Torque 100 pounds of force is applied at the end of a lever 3 feet long. The force is applied at an angle of 90° to the lever. What is the torque produced? 90  100 lb 3 ft pivot

Torque Calculation 90  100 lb 3 ft pivot

Image Resources Microsoft, Inc. (2012). Clip art. Retrieved from microsoft.com/en-us/clipart/default.aspx