Rotational Mechanics... Hinges and Normal Reactions -- Please help Could any one please explain me the reason for two normal reactions on a hinge attached to a door. Also if there are two hinges the direction of the horizontal component of normal reaction is opposite to the direction of the horizontal component for the lower hinge...why is that? It would be a great help if you could answer the above two questions in detail..... Also if there is a single hinge with a rod attached to it how do the hinge reactions vary as the rod moves in a vertical circle.... no one has been able to give a satisfactory reply to these above question's. .It would be a great relief to get these concepts cleared...Thank you..