January 18, 2002 Humpty Dumpty Grandpa Doug and his Forensic Tests!
Humpty Dumpty ran down the wall,
Humpty Dumpty had a great fall!
What is this? Six stitches in the eyebrow and a puffy eye. (This picture was taken Monday January 14th.)
Plus this huge bruise on my bicep. And more bruising under the arm and arm pit that you can't see. This was taken Tuesday afternoon. Happened on a run. Took the same off and on short cut I have occasionally been doing for nigh on 25 years. Simple zoom down and then run up the other side of a concrete drainage ditch. Always very careful when it is muddy or even drizzling as I would not want to slide down uncontrolled for probably 15 feet (on an estimated 30 degree concrete ski slope). Note that when wet, one just bypasses the concrete ramp and the use adjacent rocks as steps. However, when dry it is fun to run down the slope and build up momentum for a quick zoom up the other side.
Totally DRY on Monday morning. Exception was the city painted the graffiti over and dumb Dougie didn't even think how that might change the dry coefficient of friction. Barf! Got myself stopped before I hit the bottom of the ramp, but obviously hit a lot harder than what I initially thought. After I picked myself up and climbed up the other side (after cursing 20 times in 3 seconds) I put my hand up to feel if a bump might already be forming on my noggin and it was gooey and wet. Yuk! Never have been cut to the bone. A new experience! Worse initial pain was the sort of road rash sliding burn on my right hand palm and fingers (flat outstretched hand) that I used as part of the brakes. No visible road rash on the hand however and the stinging subsided that afternoon. Shoulder is the only thing that hurts at all now. That and being ugly. Asked the lady doctor who was sewing me up if this might screw up my chances with dating Angelina Jolie (Tomb Raider hottie). She said "no, Harrison Ford with his little scar is still very sexy."
I know you can "feel my pain" (Hah!).
Anyway today I went over to the ditch to do some coefficient of friction tests on the painted vs unpainted concrete to confirm my expectations. Here are the forensic results!
This was taken Friday morning January 18th. The 6 stitches came out the same afternoon! Here you can see the big bruise, the bruise under my arm and the slight bruise on the side of my ribs. The scene of the "stupid". (I hate the word accident. It should be removed from the English language! Why do people refuse to acknowledge that they did something stupid. Take some responsibility for your actions folks. Hey everybody - I did a "stupid".) The newly painted area that I slid down totally out of control. Scarface Doug and his "laboratory test equipment". One of the running shoes I was wearing that day and a water spray mist bottle. Physics lesson: You can measure the coefficient of friction between any two objects by gradually increasing the tilt angle of the slope at which one object starts slipping. The coefficient of friction then equals the arc tangent of that slope (when the weight started sliding). Unfortunately I can't adjust the tilt of this concrete slope to find that maximum.
Here is the dry shoe on dry unpainted concrete. No slippage means that the static coefficient of friction has to be at least .6 (to not start sliding down this estimated 30 degree slope). Not bad. Here is the dry shoe on the dry, but painted surface. Would have been thrilled to see it start sliding on its own but it didn't. Meaning again that the coefficient of friction is at least .6. MMM! So the reason for the slip and fall is not as clear as I had hoped for. The conclusion may have to be that maybe I am getting old and uncoordinated? Nah!
Next let's compare wet surface to dry: Spray some water on the painted surface.
And spray more water on the bottom of the shoe. The wet shoe on the wet surface still has no tendency to start moving on its own! However, it takes a lot less force to get the shoe started moving downhill, meaning that the wet (lubricated) friction (traction) is less than when dry - as expected. Was chicken to step on the sprayed surface to "see" if I would start sliding. Should have wet the surface 1 foot above the bottom and did that test. I know my feet would take off from underneath me. From previous experience I know that when wet, I can "ski" down, but never have enough traction to climb up. Have to always use the rocks on the side. Getting late. Have to get up early tomorrow, Saturday the 19th to drive to the Ortega mountains for a 7.2 mile trail run - part of the Winter Trail Running Series.
Then Karen and I are off to little Sierra's Second Birthday party in the afternoon!
