Answer:

Step-by-step explanation:
Given that,
Mass of a person, m = 72 kg
Force acting on a doorknob, F = 5 N
The doorknob is located 0.800 m from axis of the frictionless hinges of the door.
The angular acceleration of the dor, a = 2 rad/s²
We need to find the moment of inertia of the door about the hinges.
The person applies a torque to the door and it is given by :
...(1)
Also, the torque is equal to :
...(2)
From equation (1) and (2) we get :

I is the moment of inertia

So, the moment of inertia of the door about the hinges is
.