The physics of the wet-dog shake

Nature : Furry mammals appear to be extremely efficient at shaking water from their fur to dry themselves. In cold climates, being able to dry quickly with a minimum of effort can be crucial to survival. To study the shaking motions of some 16 different species, researchers at Georgia Tech in Atlanta used a hose and a high-speed video camera. They found that a wet bear shakes at about 4 times per second, a dog at about 6 times per second, and a mouse at a phenomenal 30 times per second. The smaller the animal the faster it has to shake to achieve the centrifugal force necessary to break the surface tension between the water droplets and its fur. Also, animals with looser skin don’t have to shake as hard as those with tight skin. The natural shaking technique of mammals is being studied because it could have many applications, including on a future Mars rover to shake dust from the electronics.