Her professional interests are in neurophysiology and psychiatric disorders. She recently obtained her PhD and is pursuing her love of science and writing at the same time. She often blogs in the third person. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue.
See Subscription Options. Discover World-Changing Science. Minetti et al. Figure 1. The other part of figure 1 So why can't humans? The other thing you could try is reducing gravity. Or, if you want to ensure success Can we build a new normal? Guest Post 6! Get smart. Sign up for our email newsletter. Sign Up. Read More Previous. These devices work in two ways they either increase buoyancy, or they use a force called dynamic lift, according to John Bush, an applied mathematician at Massachusetts Institute of Technology.
Most of the patented devices are designed to increase buoyancy, and are a take on da Vinci's classic, pontoon-ski design. Some have modifications such as bungee cords to keep the water walker's legs from splitting apart, or hinged rudders for steering and stability. Most patented water-walking devices use a light buoyant material, such as Styrofoam or wood. Dynamic lift, on the other hand, requires an outside force acting on the human body. A force is needed to pull the body in a direction parallel to the water's surface, explained Bush.
If the feet are angled properly, water flowing past the body will effectively exert an upward force that elevates the barefooter out of the water. To make fake water striders with larger and smaller surface areas, I formed the wire into flat circles of different diameters. How many pieces do I need? I could test two groups — small and large circles. I need to test each size many times, and I also need to test more than two sizes.
So I cut 60 lengths of wire. I tested five different circle sizes, and tested each circle size 12 times. For a cm piece of wire, the largest complete circle I could make was around 55 to 60 mm across around 2 inches. The smallest was 18 to 20 mm across around 0. My middle sizes were around 30, 40 and 45 to 50 mm. Because I made them by hand, they all varied slightly.
I used a big, flat book to squish each circle as flat as possible. I wanted to make sure they all had the same chance to sink or float. How much area do these circles contain? In this equation, the radius is squared or multiplied by itself. All you have to do is plug in the radius of your circle. My largest circle has an area of around 2, square mm or almost 4 square inches. My smallest has an area of around square mm 0. The three sizes in between had areas of , 1, and 1, square mm between 1.
Then, I placed each circle gently onto my tray of water. Did it sink or float? I noted which sank and which floated, for all 60 of my wire circles. I organized my data into a spreadsheet. I noted how many circles in each group sank or floated. Then I converted each number to a percentage. For the smallest circle size, only eight percent of my circles floated one out of For the largest circle size, percent of the circles bobbed neatly on the surface.
As my circles increased in area, the percent that floated also increased. What does this mean for my hypothesis? Does it mean that larger circles float more often than smaller ones? It looks like it.
This line shows the equation that would give me the slope of my line. It also shows me an R 2 value. This is a measure of how well the size of my circles correlates with whether they sink or float. The closer an R 2 value is to 1.
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