Parkour: you've probably heard of it, maybe you've seen it, odds are you've seen it or a funny spoof of it somewhere on TV or the internet. Essentially it's people doing insane flips, jumps, and stunts off of buildings, rails, and really pretty much anything, and coincidentally there are some aspects of physics that make it possible. A while back, I got my first actual parkour experience. My older brother, who lives in Virginia, took me to a parkour gym he goes to when my family went to visit him. I was so excited, and had always wondered how people do all those crazy stunts, landing from two stories high and continuing to run like it's nothing. what I discovered was not only that it's a ton of fun, but what makes it work is actually quite fascinating. Basically it all comes down to one thing, keeping your momentum going. This is done through what I was told is one of the most important things in parkour: the roll, what you're supposed to do upon landing from a large height. just hitting the ground and stopping is, well, painful to say the least, as the momentum you build from the fall goes to zero the instant you hit the floor. that much of a change in momentum in such a short time means a very large, and painful force. instead, what the roll does is extend the impact time, and transfer momentum from the fall to a different direction. the downward momentum built up from the fall is converted to rotational momentum as the person lands, then back to translational as they get up and keep running. this combination of less of a change in momentum, and more time for the impact to occur, results in significantly less force felt by a person, making all these crazy jumps and drops possible