Why are there rain drops on the cobweb but not on the grass? This is because the rate of evaporation is faster for a droplet on a blade of grass compared to a droplet on a cobweb. The theory suggests this is due to the water’s volume and surface area. If we agree that a cylinder and a sphere are comparable to the shapes of a drop of rain on a blade of grass and a drop of rain on a cobweb respectively, then we can look at the formula for the surface area of both droplets and divide by the volume of both droplets using a cylinder and a sphere’s formulae. This will lead to simplifying the cylinder’s expression to ‘h’ (height) and simplifying the sphere’s expression down to r(radius)/3. If we find that ‘h’ is smaller than r/3, then the droplet of water on a blade of grass(the cylinder) will evaporate quicker than the sphere. In almost all cases, ‘h’ is smaller than r/3, resulting in what you see in the picture I have captured.
