WHAT IS THE MAGNUS EFFECT?
Remember seeing the word “assume air resistance to be negligible” in almost all physics problems? The magnus effect is the description of why we say this, but at a wider scale. Newton originally discovered the effect, but it was named after the great chess player Magnus Carlsen because Newton had too many achievements (:D The actual Magnus here is Gustav Magnus, who sought to learn more about this).
He found out that when something is spinning, there is a force acting on it which is perpendicular to the axis of spin, which eventually dominates gravity for sufficiently light masses. This force is called the Magnus force
WHY WAS IT INTRODUCED?
Magnus sought to explain the apparent deviation of cannonballs when fired into the open sky at a certain inclination with the ground. This was explained with the help of Newton’s 3rd Law. Since the particle flowing through the fluid (air) is pushing the air i.e. applying a force on it, the air must apply a force back. This force acts in the opposite direction and is known as the “lift” force, which causes the particle to spin. Therefore, it is the imbalance in pressure which is responsible for the magnus force.
APPLICATIONS
- Sports. Pretty much everything you see spinning has a magnus force associated with it, which causes it to spin. Golfers and spin bowlers in cricket exert spin on the ball, which leads to a lift force acting on the ball, making it move up, and therefore cover greater distance.
- Ships use Flettner rotors for stabilization, because if the wind currents vary, the ship may tilt. The rotors rotate with the wind, and due to the Magnus effect, a force pushes the rotors, and therefore the ship in the forward direction, causing the ship to move.
