Arotating door is made from four rectangular sections, as indicated in the drawing. the mass of each section is 86 kg. a person pushes on the outer edge of one section with a force of f = 80 n that is directed perpendicular to the section. determine the magnitude of the door's angular acceleration.

The moment of inertia about the axis will be given by the formula;
 I0=(1/3)mh², where m is the mass of a section and h is the distance to outer edge.
Therefore, with four sections combined the inertia will be;

         4×I0 = (4/3)mh²
But Tor(M)que applied to the door is 
Torque = F × h
Therefore, 
M = I0 × x
x = M/I0   (But M =Fh
  = (Fh)/(4/3 × mh² ( simplifying the equation)
  = 3F/4mh
 but F = 80 N, m= 86 kg and i assume the height is 1.2 m

 Therefore; 
                  = (3×80)/(4×86×1.2)
                  = 0.581 rad/s²

The objects are acted upon by only one force. gravity. mass times the acceleration of gravity (-9.81meters/second squared).

The radiation of the fire causes the saucepan to heat up. the conduction of the saucepan then to distribute the heat over the saucepan and to give heat to the water. the convection of the water distributing the heat within the water, till all the water is boiling