Monday, December 7, 2015

Laying out and Sliding kinematics

As some people may know, I play a lot of Ultimate Frisbee and am one of the captains on the team this year. Something I'm quite good at, and have gotten a reputation for, is laying out for some pretty sweet catches and blocks. Since conditions in outdoor sports are variable, I wanted to figure out what my coefficient of friction was with the ground in both dry and wet conditions, and how far I landed from the point at which I left my feet. This can be solved by simple use of kinematic equations we learned in the first half of the semester.

My top speed at full sprint (unfortunately I can’t hold this for more than a few seconds) is 9.0 m/s. With this we can solve for the deceleration I experienced, as well as time.

vf^2=vi^2+2ax, for distance after I hit the ground. Normally, I slide about 1.5 meters on dry grass, and 4 meters on wet grass.

With the acceleration, we can then find the force of friction, and use that to find the coefficient of friction with the ground for both wet and dry conditions.
F=ma=mgu

Since I tend to position my body such that I fall 1 meter when I dive, we can also find the force that I experience when I hit the ground, as well as how far I travel in the air.

F=mg, y=.5at^2, x=vi*t
Results:
a dry= -27 m/s2, a wet= -10.125
u dry = 2.76, u wet= 1.03

Fground=666.4 N, time of falling=0.45 seconds, distance in air: 4.05 meters