The Magnus Effect

The tendency for an object to follow a curved path instead of a straight one is known as the magnus effect.

This is due to the generation of a side wards force on a spinning spherical or cylindrical object known as the Magnus force.

The mechanism.

The mechanism is rather a simple affair – As the rotating object moves through the air, it pushes the air on side of the ball whilst disturbing and slowing the flow on the other side down.

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What this does is, it creates a pressure differential. Faster moving air exerts lesser pressure and slower moving turbulent air exerts a higher pressure. And as a result, the ball experiences a force ( known as the magnus force ).

This force vector points from the higher pressure region to the lower pressure one.

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The Aerofoil similarity

If you think about it, it is the same principle as a lift in an aircraft. ( the difference off course lies in the fact that for the Magnus effect to take place, the object must spin )

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More the pressure differential, more the lift.

Now an obvious question might strike your mind – What if the wings rotated? I present to you the Flettner Rotor Aircraft which whose wings rotate in order to generate lift.

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But sadly, the drag that these things produced were also considerably high rendering them impractical! Ahh..

( If you are interested, check out the No sail boat that Flettner built that actually works and uses the magnus effect )


Magnus effect in sports

Magnus effect underlies various sporting action. For instance that spectacular Ronaldo’s free-kick was a consequence of the magnus effect.

Cricket – Spin Bowling.

Notice the change in direction of the ball during flight.

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Tennis – The dreaded Topspin

The ball experiences a downward push as a result of magnus effect.

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Baseball – A pitcher’s delight

This pitcher just knows how to rule the game.

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You get the idea, right ? Basically, any sport that involves a rotating body, you are most likely to find the magnus effect coming into play.

Have fun exploring this effect in your own unique way and as always have a good one! Cheers!

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Useful Links:

The magnus effect and the world cup football

How to make a cup that flies.

Flettner‘s No sail Rotor Ship

PC: Royal Institution, Cosmol

*** The phenomenon simplified for the sake of explanation. For those who are seeking out answers from a fluid mechanics and mathematical perspective ( boundary layers, flow stagnation,etc ) check out any standard Fluid mechanics Text.

Celestial Wonders- Binary Stars.

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The twins of the stellar world are binary star systems.A binary star is a star system consisting of two stars orbiting around their common center of mass.When two stars appear close together in the sky, the situation is known as an “optical double”. This means that although the stars are aligned along the same line of sight, they may be at completely different distances from us. This occurs in constellations; however, two stars in the same constellation can also be part of a binary system.

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Artist’s impression of the sight from a (hypothetical) moon of planet HD 188753 Ab (upper left), which orbits a triple star system( yes, a Triple Star system!). The brightest companion is just below the horizon.

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Binary star systems are very important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined, which in turn allows other stellar parameters, such as radius and density, to be indirectly estimated. This also determines an empirical mass-luminosity relationship (MLR) from which the masses of single stars can be estimated.

It is estimated that approximately 1/3 of the star systems in the Milky Way are binary or multiple, with the remaining 2/3 consisting of single stars.

The Brightest star in the sky is a binary.

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This is true. When it was discovered in 1844 by the German astronomer Bessel, the system was classed as an astrometric binary, because the companion star, Sirius B, was too faint to be seen. Bessel, who was also a mathematician, determined by calculations that Sirius B existed after observing that the proper of Sirius A (the main star) followed a wavy path in the sky, rather than a uniform path. Sirius can now be studied as a visual binary because, with improving technology and therefore improved telescopes, Sirius B was able to be seen, although not for 20 years after Bessel had correctly predicted its existence.

Black Holes in a binary System ?

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The term “binary system” is not used exclusively for star systems, but also for planets, asteroids, and galaxies which rotate around a common center of gravity. However, this is not a trick question; even in star binaries, the companion can be a black hole. An example of this is Cygnus X-1.

The universe is pretty amazing huh?…

Why don’t rain drops kill you?

Pardon me for being melodramatic. Think about it, rain drops fall from thousands of feet in the air and yet we hardly twitch when one falls on us.This defies all logic, if you drop a penny from the top of a building and let it fall on you, we know that it hurts!
Have the angels cast a magical spell on the rain drops to spare us from the pain?

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Terminal Velocity.

When you drop something in air, it does not accelerate forever. Molecules in air constantly bombard with the object, exerting an upward force. This is known as air resistance or drag.

As the object gains velocity there comes a time when the force of the air resistance is enough to balance the force of gravity, so the acceleration stops and the raindrop attains terminal velocity.

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Terminal Velocity is the maximum velocity an object can travel in air!

The Angel’s mystical spell.

Rain drops are only 0.5 mm-4 mm in diameter. Their terminal velocity is only about 10 m/s ( 20 mph ) That’s the maximum speed that they can travel in air irrespective of their initial height. Also the mass of the rain drop is about a few milligrams.

Hence, the force that it exerts on the body is really small, small enough that we find the experience pleasurable and soothing.

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