Trying to push a wheelchair up the sloped edge of a sidewalk?

I see two principles at work here:

• Large wheels handle bumps more easily than small wheels.

• You are less likely to tip over if you go up a slope backwards.

(Your center of mass is in a more stable position.)

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When you hit any bump, the force of the bump is directed toward the hub, where the axle is. For a smaller wheel, this force is directed more horizontally. This works in opposition to the direction of motion, and can really slow you down. For a larger wheel, the force is directed more vertically -- you get a bumpy ride, but the forward progress is far less affected. This is why Conestoga wagons had such large wheels compared to traditional wagons that travelled on smoother roads. For a wheelchair, it is easier to meet the slope with the larger wheel -- i.e, go backwards.

Another consideration is where your center of mass winds up. Most of your weight is just barely in front of the axle of large wheel. If you go up a slope frontwards, as the chair tips backwards, your center of mass might move behind the axle, causing the chair to tip over backwards -- very dangerous! If you go up a slope backwards instead, then your center of mass moves forward to between the wheels of the chair, and the chair becomes more stable.

Men and women have different body mass distributions. Leg amputees have a center of mass farther back than other users. Because of this, most chairs have a wrench adjustment to move the axle attachment point forward or backward a bit, to customize it for the user. Part of fitting a wheelchair is setting this properly for each user -- maybe this was not done for you, and consequently you had some extra difficulty in using the chair.

My brother uses a wheelchair. He often has to turn around and go up things backwards. He also is an expert at popping wheelies. When he meets a small curb or small rise, he gets up some speed then pops a wheelie just as he meets the obstacle. The front wheels just fly over the obstacle. Then he leans forward a bit and pushes hard as the large back wheels meet the obstacle. So, athletic and skilled users have more options.

Yes, engineers and therapists take physics. I have seen them in my classes. Most of them even do well. I don't think anyone is doing anything wrong in this case. I'm guessing it is far easier to use the ramps provided than it would be to jump the curb directly -- I'm not sure what else you could do.

P.S. I am glad you are back on your feet.