Why it gets easier to push open a door, the further you are from the hinge?
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Note: upon rereading, maybe that my memories of work are incorrect and that I may have mixed it with energy. To ease comprehension without learning wrong premices about physics, assume that “work” is more a concept, rather than the scientific term.
Let’s try this approach:
To open a door, or even, to do anything, you need to perform some actions in order to complete a task. A task will require a certain amount of **work**.
The course of action to open a door will require you to expend energy to push the door. In other terms, it requires a certain amount of work to open it. This amount is generally fixed, I mean your door doesn’t randomly become harder or easier to be opened each and every time you do, does it?
Now, to successfully open it, you need to meet the amount of work required to do so. Assuming the door has no locks, you can do it in a lot of way:
– you can traditionally push it by the knob, which will require some force along some distance to be done;
– you can lean against it, the gravitational pull of Earth will generate much more work than needed to open the door, thus slamming the door against the wall and you slamming on the floor flat;
– you can kick it, your body will also produce much more work than needed to push that door open, which will slam hard on the wall.
But, why opening it by pushing near the hinge is harder? Remember, the amount of work to open the door is constant. We’ve stated that, opening the door along the knob requires a fixed amount of force along a fixed distance. The distance is big, since you push the far end of the door all the way to opened, and the force is of some quantity. If you push the near side of the door open, you drastically reduce the amount of distance you have to go, since the radius is now a few inches. But the amount of work needed is still the same to open the door, so to compensate a **shorter** distance, you need a **bigger** force.
Easy example: 20 * 5 = 100. But if suddenly 20 becomes halved, 10, then 5 needs to be doubled, so it becomes 10. 10 * 10 = 100.
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