This Video Shows How a Lawnmower Cuts Grass in Incredible Slow Motion
As summer warms up, keeping the lawn nice and neat is a weekly task for many people. But how does a lawn mower actually cut grass?
Unlike the most common cutting tool, scissors, lawn mowers don’t use two opposing blades to create a shear stress at a localized point. They instead have a rotating blade inside a metal housing case.
The enthusiastic host of Smarter Every Day was intrigued by the physics involved in cutting grass. Wondering why it is that grass can be cut at all with this seemingly ineffectual method.
Luckily he has a super fast camera and some equally enthusiastic friends to help solve the mystery. The first part of the mystery was solved by a visit to the local barber shop who pointed out that an ordinary lawnmower sucks air up into the mower body causing the grass to stand vertically, which allows the blade to slice evenly at the bottom of the grass.
To demonstrate this in another way, a vacuum hair clipper does the same thing. It sucks hair into it before it is cut so that a really precise cut can be made. The lifting of the grass is actually caused by the tab on the back of the mower blade which causes air lift and raises the grass up.
By filming a lawn mower in action with a super fast camera, that in turn gives wonderful slow motion, you can see the blades of grass being lifted up just before being cut. Another mystery solved by the informative Smarter Everyday team.