Sometimes you think you have a complete understanding of something and then BOOM—a simple problem throws everything out the window. Let's consider a very basic physics problem involving pushing a ...

Friction is an intrinsic physical phenomenon to curling. Without it, objects in motion would move endlessly, without slowing down. This would cause many safety-related problems: Cars or trains could ...

As one gear turns, the other gear must also turn. Where the gears meet, the teeth must both move in the same direction. In the diagram, the teeth of both gears move upwards. This means that the gears ...