Question

The rotor of an electric motor has rotational inertia Im = 4.54 x 10-3kg.m2 about its central axis. The motor is used to change the orientation of the space probe in which it is mounted. The motor axis is mounted along the central axis of the probe; the probe has rotational inertia l = 14.3 kg.m² about this axis. Calculate the number of revolutions of the rotor required to turn the probe through 18.4° about its central axis. Number Units

Answer 1

Given that

motor's rotational inertia Im = 4.54*10^-3 kg.m^2

probe's rotational inertia Ip = 14.3 kg.m^2

$\theta$ = 18.4 degree

using conservation of angular momentum

Im*$\omega$m*t = Ip*$\omega$p*t

where $\omega$ m*t = 2$\pi$n = 360n

and $\omega$ p*t = 18.4 degree

4.54*10^-3 *360n = 14.3*18.4

n = 160.99 = 161 Revolutions

Good Luck !