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 ...

1.1 What is friction? Take this everyday example: when a coffee mug rests on a flat table, the kinetic frictional force is zero. There is no force trying to move the mug across the table, so there is ...

It’s a moonless night. The wind howls outside. A door opens slowly, as if pushed by an invisible hand. “Cre-e-e-a-k.” That sound — a horror movie cliché — is the result of friction. A stealthier ...