Red Bull Physics: Trains, Bikes, and Inertial Reference Frames
Just in case you didn’t know, there’s some crazy awesome stuff online. In this case it’s a video from Red Bull showing Dawid Godziek riding on a mountain bike track. But wait! The track is on a train and the train is moving. It’s just great. Check it out.
But how does this work? Is it possible to jump a bike on a ramp that’s also on a moving train? I mean…hello? Did you watch the video? Yes, it’s possible.
Here is my super short explanation of how this works (followed by stuff for my classical mechanics course). We can model the motion of an object using Newton’s second law. This says that the acceleration of that object depends on the net force acting on that object.
So, if you drop a ball there will be a downward gravitational force acting on it (mg). You can use this to find the acceleration of that object and from that the position of the object as a function of time (the equation of motion).
However, Newton’s second law only works in an inertial reference frame. You can picture this as a set of…
