
Thyroid gland do not secrete
Considering a gas in a parallelopiped, in a small time interval , a molecule with x-component of velocity will hit the wall
Collision by moleculeto the wall of conntainer assumed to be perfectly elastic.
By the principle of conservation of momentum, the momentum imparted to the wall in the collision = 2mvx
So the magnitude of the force on the wall from each collision is
distance travelled in time