The locus of the door- handle, as the door opens.

There are 2 locks on the door and the door keys are among the 6 different ones you carry in your pocket . In a hurry one key is dropped somewhere by you. The probability that you can still open the door is

Spring fitted doors close by themselves when released. You want to keep the door open for a long time, say for an hour. If you put a half kg stone in front of the open door, it does not help. The sotne slides with the door and the door gets closed. However, if you sandwitch a 20 g of wood in the small gap between the door and the floor, the door stays open. Explain why a much lighter peice of wood is able to keep the door open while the heavy fails.

The iron door of a building is 3m broad. It can be opened by applying a force of 100N normally at the middle of the door. Calculate (a) the torque needed to open the door, (b) the least force and its point of application to open the door.

A vertical rectangular door with its centre of gravity at O (see figure) is fixed on two hinges A and B along one vertical length side of the door. The entire weight of the door is supported by the hinge A . Then the free body force diagram for the door (the arrows indicate the direction of the forces) is

A man opens a nut by applying a force of 150 N by using a lever handle of length 0*4m . What should be the length of the handle if he wants to open it by applying a force of 60 N?