a helicpoter has 2 blades. each blade has a mass of 240kg and can be approximate
ID: 1301474 • Letter: A
Question
a helicpoter has 2 blades. each blade has a mass of 240kg and can be approximated by this rod of length 6.7 meters. these blades are rotating at 44rad/sec.
a) what is the total moment of inertia of the two blades about the axis of rotation?( hint( total I= 2 I each blade)
b) find the final rotational kinetic energy of the two blades
c)how much torque is needed to bring the blades up from 0rad/sec to 44rad/sec in 10sec?
d) how much power is required to generate the final angular speed of 44rad/sec in 10sec?
Explanation / Answer
M = 240 kg
L = 6.7 m
a)
MOI of each blade = ML^2 / 3
MOI of 2 blades = 2ML^2 / 3
b)
w = 44 rad/s
KE = 1/2*I*w^2
= 1/2 * (2/3)*ML^2 * w^2
c)
alpha = (44 - 0) / 10 = 4.4 rad/s^2
Torque = I*alpha
= 2/3*ML^2 *4.4
d)
Power = Torque*w
= 2/3*ML^2 *4.4 *44
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