Question

A propeller is modeled as five identical uniform rods extending radially from its axis. The length and mass of each rod are 0.803 m and 2.61 kg, respectively. When the propellor rotates at 577 rpm (revolutions per minute), what is its rotational kinetic energy?

Answer 1

L=0.803 m
M=2.61 Kg

Moment of inertia=Ml^2/3
                 =0.803*(2.61^2)/3
                 =1.823 Kgm^2
Such Five identical rods are there

Total moment of inertia=5*1.823 =9.12 Kgm^2

angular velocity=577 rpm
                =577*2*3.14/60
                =60.34 rad/s

ROtational kinetic Energy= 1/2* I * w^2
                         =0.5*9.12*60.34^2
                         =16602.6 J