Spaces and dimensions

What do mathematicians and physicists mean with phrases like higher and/or extra dimensions? Let’s travel through a Universe of spaces and dimensions!

Finding the normal force in planar non-uniform circular motion using polar coordinates

We find an expression for the normal force on a mass which is in planar non-uniform circular motion using polar coordinates.

Mirror, mirror, what’s up with the mirror writing?

We see a monkey holding a mirror and looking in it, looking at itself.

Ever wondered why sentences, words, and letters always exclusively seem to have their left and right reversed in the mirror, while they are almost never projected upside down? Probably, because mirrors do something else than you would expect. For starters, mirrors don’t reverse left and right.

Just a minute: Minus minus and negative times negative

A photoshopped image of an out-of-focus dude with a beard holding a little sphere between his thumb and index finger in front of his face. The little sphere has a plus-sign on it. There are multiple spheres floating around with a minus-sign on them. Have a lovely day today!

Minus minus is plus. And negative times negative is positive. Two negatives make a positive. You may have heard or uttered these expressions many times. Even though you will know this already, here you will find an algebraic proof, just for your reference. Requirements: simple algebra from the second year in secondary, high or grammar school.