Answer:
0.2 m
Explanation:
m = mass of the rotor of an electric motor = 26 kg
R = radius of gyration = ?
magnitude of moment of inertia is given as
I = m R²
w₀ = initial angular velocity for rotor = 0 rad/s
w = final angular velocity of rotor = 3600 rpm = (3600) (2π/60) = 376.8 rad/s
t = time interval = 4.2 min = 4.2 x 60 sec = 252 sec
α = angular acceleration of rotor
Using the equation
w = w₀ + α t
376.8 = 0 + α (252)
α = 1.5 rad/s²
τ = magnitude of couple = 1.2 N-m
magnitude of couple is given as
τ = I α
τ = m R² α
1.2 = (26) (1.5) R²
R = 0.2 m
