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A typical small rescue helicopter has four blades, each is 4.00 m long and has a mass of 50.0 kg. The blades can be approximated as thin rods that rotate about one end of an axis perpendicular to their length. The helicopter has a total loaded mass of 1000 kg (including the four blades). (a) Calculate the rotational kinetic energy in the blades as they rotate at 300 rev/min.

Answer :

Answer:

I1 = 1/3 m L^2 = 50 * 4^2 / 3 = 267 kg-m^2     inertia of one blade

I = 4 * I1 = 1067 kg-m^2      inertia of rotor

f = 300/min = 5 / sec

ω = 2 pi * f = 31.4 / sec

KE = 1/2 * I * ω^2 = 526,000 J      energy of rotor

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