Why it gets easier to push open a door, the further you are from the hinge?
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A door is a simple machine. Particularly a wheel-and-axel and lever. When you have a lever, the further you are from the fulcrum -the point of contact of the seesaw- the less effort it takes to move the opposite side. In this case the hinge is your fulcrum, therefore the opposite side is easiest to move.
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Think of it like playing on a teeter totter. If you’re closer to the center, you can’t really lift your friend up unless you jump really hard or maybe you’re the biggest kid around and can do it because you weigh more. Opening the door closer to the hinge is like sitting closer to the center of a teeter totter.
If you’re on the playground and want to balance a teeter-totter, you have a few options to play around with if the weights don’t line up right. Move kids on the heavier side further towards the middle, or kids on the lighter side towards the edge, and it can balance things out.
A door is basically a teeter-totter where the other “side” is gravitational inertia. A heavy door takes a lot of force to move, but being further from the hinge gives you a lever to act as a force multiplier for your movement.
Remember the last time you were on a see-saw? Did you notice it takes more effort to push yourself up, and a smaller distance, when you were sitting closer to the middle of the see-saw? But if you sit on the very end it’s very easy and you can jump really high with less effort. A door is very similar to a see-saw and the door hinge is like the middle of the see-saw where it rotates.
Same reason why it’s much easier to clip your nails squeezing the end of the top lever of a nail clipper opposed to the blade-end. More length=more leverage and torque output for the same amount of energy in.
The same physics apply for the door except now we’re factoring in the weight for the entire height of the door.
It functions as a lever. The further you are from the hinge the more leverage you achieve which means less force is needed to open the door.
The door acts as a lever, providing mechanical advantage in the form of leverage. The force applied is multiplied by the distance from the hinges.
Why does it get easier to push on a lever the further you are from the fulcrum?
It’s not easier. You’re just doing the same amount of work over a larger distance. If you’re pushing at the hinge your push length may only be a few inches so in order to move the whole door you need to apply a lot more force to get the same amount of work. If you’re on the outside edge of the door you’re pushing the door a number of feet and thus can apply less force for that amount of work.
Work = Force x Displacement in the direction of the force applied.
It’s the same amount of work in either case but if the displacement goes down the force has to go up.
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