Pushing through sand
For those of you who take sandcastle building very seriously, listen up: MIT engineers now say you can trust a very simple equation to calculate the force required to push a shovel — and any other “intruder”— through sand. The team also found that the same concept, known as the resistive force theory, can generate useful equations for cohesive materials like muds. Aside from calculating the elbow grease needed to carve out a beachside moat, the researchers say the equation can be used to optimize the way vehicles drive over gravel and soil, such as rovers navigating the Martian landscape. It can also help illuminate the ways in which animals such as lizards and worms burrow through earth. Resistive force theory (RFT) is not new and in fact was proposed in the 1950s to describe the way in which objects move through viscous fluids such as water (on small scales) and honey....