Coordinate systems in physics

Today I'd like to talk about one of the most overlooked and simple things you can do in your physics class to improve your grades and understanding. Physics students often leave out the coordinate system when writing out a problem, and it’s not ok. What is a coordinate system? It's an x-axis and/or y-axis depending on if you're in one or two dimensions. Coordinate systems are a way of communicating location. If I ask you “where am I”, you can't just say over there. You have to say something like you're 5 feet from this wall and 3 feet from that wall. You can never talk about location without first defining a frame of reference. A frame of reference will be defined by a coordinate system so it's really important that in every physics problem the first thing you do is draw a coordinate system. Most students skip this step because they don't see why it's important. One thing that students love to do is say that the acceleration due to Earth's gravity is -9.8 m per second squared and they just think that it's inherently negative, but it’s not. The acceleration due to Earth's gravity will always and forever be pointing towards the center of the Earth, but that’s not what makes it negative. It’s your choice of coordinate systems that make it negative or positive.