Impulse

I never stopped to realize that karate has something to do with physics. Every time I throw out a punch, I am exerting an impulse that is equal to the amount of force I put in to the punch multiplied by the amount of time I exert that force for. Impulse is equal to the change in momentum. Punching someone is almost like a sticky collision and momentum is conserved no matter what, so the initial momentum should equal the final momentum. Also with this in mind, almost all of my punches exert the same impulse, but the stronger punches are the ones with more force done in less time, rather than the ones done with less force in more time, so quick jabs are much more effective in sparring. I always knew that fast punches seemed much stronger than the ones I took my time on, but I never knew the reasoning behind this until we recently started learning about momentum and impulse.

Potential and Kinetic Energy

In class, we are learning about potential and kinetic energy. At the top of the slide before I started sliding down, my potential energy in relation to the bottom of the slide is equal to my mass times 9.8g times the height from the top of the slide to the ground. My kinetic engery at this moment is zero because kinetic energy is equal to half of my mass times velocity squared, and I have zero velocity. As I started sliding down the slide, my kinetic energy raised because I was gaining velocity, but my potential energy lowered because the height was lowering. Althought the potential and kinetic energy was changing as I slided down, the total energy (potential + kinetic) remained constant at any point. This explains the conservation of energy. At the bottom of the slide, I came to a stop and my potential and kinetic energy both became zero.