A helicopter has two blades (see figure), each of which has a mass of 220 kg and

Question

A helicopter has two blades (see figure), each of which has a mass of 220 kg and can be approximated as a thin rod of length 6.7 m. The blades are rotating at an angular speed of 44 rad/s. (a) What is the total moment of inertia of the two blades about the axis of rotation? (a) Determine the rotational kinetic energy of the spinning blades.

2,A bowling ball encounters a 0.760-m vertical rise on the way back to the ball rack, as the drawing illustrates. Ignore frictional losses and assume that the mass of the ball is distributed uniformly. The translational speed of the ball is 8.32 m/s at the bottom of the rise. Find the translational speed at the top.

Explanation / Answer

(a) MOI of rod = ML^2 / 3

Total MOI = 2 x (ML^2/3)

Itotal = 2 x (220 x (6.7)^2 / 3)

Itotal = 6583.86 Kg.m^2

(b) ROtational KE = 1/2 Iw^2 (w = omega)

(KEr)total = 2 x (1/2 x Iw^2) = Iw^2 = (ML^2/3) w^2

KEr)total = (220 x (6.7)^2 / 3) x (44)^2

KEr)total = 6373182.93 J

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