PLTW Elements of Power - Elements of Power types and calculations ● ● ● ● Work is the energy transferred when a force displaces a mass Power is

# PLTW Elements of Power - Elements of Power types and...

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Elements of Power : types and calculations Work is the energy transferred when a force displaces a mass Power is the rate at which work is done Typically mechanical, electrical, or fluid (fluid power → hydraulic, pneumatic) Mechanical Calculations W = F ll * d P = W t P hp = P 550 ft lb s W = Work (measured as ft-lb) P = power (measured as ft-lb/s) t = time (measured as s) 1 hp = 550 ft-lb/s If Jessica moves her 112 pound (lbs) body up 8 feet (ft) of stairs in 2.3 seconds (s), how much work did she perform? How much power did she use? W = F ll * d 112 * 8 = 896 W = 896 ft-lb P = W t 896/2.3 = 389.6 P = 390 ft-lb/s P hp = P 550 ft lb s P hp = 390 ft-lb/s (1 hp - 550 ft-lb/s) P hp = 0.71 hp An escalator moves 84 people per minute from one floor of a mall to the second floor. The mall’s floors are 24 ft apart, and the average passenger weighs 154 lb. How much power does the escalator need? F = 154 lb/person * 84 people F = 12,936 lb W = F ll * d W = 12,936 lb (24 ft) W = 310,464 ft-lb P = W t P = 310,464 60 P = 5174 ft-lb/s P hp = 5174 ft-lb/s (1 hp/550 ft-lb/s)
P hp = 9.4 hp

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