Question

A helicopter has two blades (see figure), each of which has a mass of 240 kg and can be approximated as a thin rod of length 6.7 m. The blades are rotating at an angular speed of 43 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.

Answer 1

Given, Each blade has mass ,

Each blade has length ,

We have to find the M.l. at axia of rotation.

Each blade can better considered to be a rod of length .

Then we can consider that we have rod of length $L=l+l$ .

Then M.l. art the center of rod of length L is

$I=ML^2/12$ , where M be combined mass pig too blades.

It gives,

(b) Rotational kinetic energy can be given as,