Thursday, May 2, 2013

Paddling a Wheeled Canoe with Sir Isaac Newton

My recovery from knee surgery was slowed by a fall a few weeks after the surgery.  I've been ambulatory without crutches or a cane for a few weeks now. However, I can’t keep a normal walking pace.

My wife’s daily walking routine was interrupted by my convalescence because she does not like to exercise alone. Actually, she doesn't like to exercise at all so if she has to do it alone it isn't going to happen. In order to get her going again I bought a wheelchair on eBay so that I could accompany her on her walk.

How hard could it be, I thought? She always walked slower than me so it will be easy to stay alongside of her with a wheelchair. Right away, I learned that driving a wheelchair is much like paddling a canoe on a lake with shifting winds.

We don’t have sidewalks in our residential area and the streets, like most, are crowned for causing rain water to run-off. This avoids having huge puddles on the pavement. It works pretty well. Though I’m not rain water, run-off of the pavement is exactly what I did.

Remembering how one steers when paddling a canoe, I considered the similarity. It can’t be that much different, I thought. Yeah? Try to do a J-stroke on the grab rim of the wheel on a wheelchair. Still, it seemed that the principle would apply and it does, sort of.

I would simply turn on the wheel of the opposite side of the direction that I wanted to go. That always worked pretty well when paddling with the current of a river. You’ll find it quite different if you try it on a lake without current to help you go forward. Add wind or, in this case, the rain run-off grade to oppose you and you’re in for a fight.

Even if I ran only one wheel, I could only slow the run-off. I couldn't stop it completely. If I dragged on the opposite wheel, then I could hold position but that was counterproductive to the intended forward motion.

Flashbacks of Newton’s laws of motion from high school science class came to me. Back then I wasn't interested in all of that stuff about objects at rest and objects in motion. Force equals mass times acceleration. Get real! Where’s the practical application to a high school student?

I soon found that, if I kept the wheelchair in the center of the street crown, then I could hold it in a straight line. However, I also became cognizant of Newton’s third law of motion that says for any action there is an equal and opposite reaction. My action of wheeling myself down the street caused the very real reaction of wearing me out. The whole humbling experience left me wondering why I ever thought that my two scrawny arms could amble me along as efficiently as two healthy legs.

As it turned out, the best way that I could accompany my wife on her daily walks was if she pushed me in my wheelchair. We’re a sight to see in the predawn darkness with a flashlight leading our way, a flashing red strobe clipped on my wife’s hip pocket and reflector tape attached everywhere on the wheelchair that I could find to stick it. The two dogs are with us with one leash in each of my hands.

My wife doesn't mind the added workout of pushing my weight. In fact, as she got back into the exercise routine again, she has increased her daily distance and decreased the time to walk it. The run-off crown of the pavement doesn't affect her forward inertia like it does me. It must have something to do with equal and opposite outside force.

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