Question

Sometimes people use magnets to keep that doors open and sometimes to close the doors Prime Li think and say how it is possible and how we should arrange the magnets in each case .

Answer 1

When we need to open the door

the repultion property of magney can be used by putting 2 like poles of magnet each on door and thing from which door is attached

Similary for closing the door attraction of unlike poles of magnet can be used