It's not. This is absurd.
Yes, a doorknob is considered a wheel and axle because when you turn the doorknob to open the door you are turning it so you can open the door.
Doorknob
As long as the door is locked on the outside, the inside door lock of a keyed doorknob will also always be locked from the inside.
Check the doorknob. A wooden door may not feel hot, even if the other side is burning (wood insulates). However, the metal doorknob, which goes all the way through the door, DOES conduct heat very well. If the doorknob is hot, so is the other side of the door.
Yes a door knob does have minerals.
A metal doorknob
A doorknob is usually placed about 3 ft off the ground and 2 inches from the side opposite the hinges I have one doorknob that is placed too close to the edge and my fingers get pinched often when I close the door.
If the doorknob were moved to the middle of the door, it would take twice as much force to open it than if it were at the edge of the door. With the mass of the door being equal. Moment = the force to open the door times the distance to the center of the hinges. If the distance were cut in half it would take twice the force to keep the equation true.
break the door
electrical energy
This will vary based on the door. Most often, the doorknob is approximately 36-38 inches above the floor.
The German word for door knob is der Türknauf.