Where You Push the Door Decides
Two identical doors, the same number of newtons applied to each, released at the same instant — one push at the handle, the other right beside the hinge. The handle side is away while the other barely stirs, and a push aimed straight into the hinge does nothing at all. Distance, not force, is what the idea of a moment was missing.
Como usar esta simulação
- Press Push both to release two doors with equal forces at different distances
- Load Handle against hinge — 0.88 m against 0.15 m from the axis
- Press Push right on the hinge to apply a force at zero distance
- Try A fair fight, 10 N far out against 60 N close in, and see which wins
O que observar
- Equal forces at unequal distances give unequal turning effects every time
- A push directed through the hinge produces no rotation whatever its size
- At the same distance the two doors behave identically, so only the product matters
- A slanted push turns the door more slowly than a square-on one of the same size
- 10 N far out can beat 60 N close in, as long as the products come out that way
A física por trás
Turning effect is the product of the force and the perpendicular distance from the axis to its line of action: M = F·d. Equal forces at different distances therefore produce quite different moments, and the one applied further out wins. A force whose line of action passes through the hinge has d = 0 and produces no moment at all, however large it is. Slanting the push by θ to the door leaves only the perpendicular component F sin θ contributing, so part of the effort is spent pressing the door against its hinge rather than turning it.