Fun Fact: If the movie Rocky had been about wheelchair boxing (yes, it does exist!) then, according to the guidelines of the Americans with Disabilities Act, the famous training montage would have climaxed with a dramatic roll up a 672 foot long wheelchair ramp to the Philadelphia Museum of Art.
Okay everybody, get yourself a board. A long board. Great. Now… lean it against something sturdy. Done? Congratulations! You’ve just constructed a “machine”… technically speaking. It’s one of the six Simple Machines that are the basic building blocks of all our tools and devices.
You may call it a ramp, or “a plank leaning on a fence”, but it is in fact an inclined plane in science talk. A plane is a flat surface (not to be confused with a plain… a flat surface covered in grass) and inclined means one end is higher than the other. Sounds simple, but like all the other simple machines, this has given you a mechanical advantage. It has made it easier to do work.
We’re talking about work in the technical/mechanical/physics way. Work is defined as the energy transferred by a force acting over distance. So let’s say there’s a big box on the floor. For you to lift that box a fraction of an inch you would have to apply a certain amount of force. Now, for you to lift that box from the floor to the table, you would have to maintain that same amount of force all the way up. That gives us the formula: Work = Force x Distance.
Now let’s get our scrap of lumber to make an inclined plane. One end is on the floor, the other end rests on the table edge. It’s easier to push the heavy box up the ramp (compared to lifting it straight up) because the inclined plane covers more distance to reach the objective. By virtue of the formula (W = F x d) to do the same amount of work, an increased distance requires less force.
The longer an inclined plane, the less force required to get to the top. That’s why some streets in San Fransisco are so curvy. They cover more distance going up a steep hill, so the car engine doesn’t have to work as hard. However, the same amount of work is done either way. It’s just a choice between light work for a long time, or heavy work for a short time.
For wheelchair access ramps, the guideline is to have a slope of 1:16. (16 inches of ramp for every 1 inch of height) That means a recommended 9 feet of ramp for every average 7-inch step of a stairway. 4 steps, 37 foot ramp. 72 famous Philadelphian steps, 672 foot ramp.
And since I know you’re curious, if the ADA wanted to make Mount Everest more wheelchair friendly, starting at base camp they would need to build a ramp over 55 kilometers in length to reach the summit.