What Is The Magnus Force?

Whenever an object spins through the air it experiences a 'Magnus Force' due to friction between the air and the object's surface. This force was originally identified while studying the trajectories of cannon balls (though earlier observations of this effect exist). The Magnus force is essential in most ball sports including golf, cricket, tennis, and baseball.

At the end the ball demonstrations were conducted with a 100 mm diam polystyrene ball and the launcher was made by bending a long, thin, aluminum rod and bolting the ends to a block of wood as a handle.

[inrain]

The Magnus Force is the force by which you get steamrolled when your name is Ian Nepomniachtchi and you play in the Chess World Championship.

[princevegeta]

Ah, air resistance, the so ignored phenomenon in physics. But magnus effect gives it life.

[FBR]

This really explains the trajectory of top spin loops and chops in table tennis

[k.mirenburg]

Great discussion. I first saw the magnus effect demonstrated in a fluids lab in 1966 when we took our first trip to third year fluids lab. We had pressure tabs around the cylinder and measured the pressure around a rotating cylinder in a modest size wind tunnel. There is a nice CFD simulation on YouTube which animates this effect in color.
Liked the professors talk.

[Tornair]

This is the kind of Physics I'm actually interested in

[billswingle]

Excellent illustration! I had no idea the paper tube would be so illustrative. Great job!

[veritasium]

@scoutmasterkb28 you could think about Bernoulli's in the region immediately surrounding the ball in which case you would say the faster moving air on one side (in the example it would be on top) results in lower pressure than on the other side so this difference in pressure puts a force on the ball - so this is a valid explanation.

[MS-pxhx]

"In chess"
When opponent is sitting right in front of world champ magnus carlsen they experience an absurd amount of mental force and that's what is called MAGNUS force.

[Merrida]

I am SO glad I subbed to you. I'm so delighted every time you post. I like learning all these wonderful things you show. Thank you so much!

[veritasium]

@someblokecalleddave1 the cricket ball has another force on it due to the seam, or later in the game due to the roughness of one side. This causes the ball to swing toward the rough side. An episode on this is coming up soon.

[nilsum]

i still don't understand the science behind people disliking these videos. who are they? seriously.

[veritasium]

@scoutmasterkb28 Nope! It's not to do with Bernoulli's because that considers only pressure, gravitational energy and translational kinetic energy, not rotational energy.

[BenjaminFunklin]

I took a class on fluid flows and we briefly covered the Magnus Effect.  I found slides from one of my lectures that the force had to do with differences in pressures on the top of the ball vs the bottom as it moves through the air.  Others have already pointed this out, but to reiterate perhaps in a different way;  as the ball moves through the air horizontally air is passes around the top most point and bottom most point of the ball equally.  Lets say you hit a topspin shot in tennis. The ball moves through the air and on the bottom of the ball the fuzz(friction) on the ball is grabbing the air and moving it faster.  On the top of the ball the friction between the ball and the air is grabbing the air and throwing it against the oncoming air wizzing past the ball.  As velocity increases pressure decreases and you have a situation where high velocity but low pressure is on the bottom of the ball and higher pressure low air velocity is on the top.  The atmosphere presses down on the ball towards the low pressure causing the ball to accelerate towards the court faster than it normally would with just gravity.  The surface of the ball and the speed can also effect if the flow around the ball making it laminar or turbulent which when combined with spin can have some interesting effects.  What makes golf balls and table tennis balls different is a good example of that. One other note that most people probably caught but anyways in the video it wasn't really explained why the cylinder moves backwards after being dropped from the plank. It's be cause the body is not moving through the air horizontally but on a diagonal initially so the fastest air relative to the cylinder is on the edge that just left the plank which caused the Magnus force to push down and back + drag as well.  

[travis]

Its a shame this isn't taught in youth sports more. I spent hundreds of hours trying to figure out to manipulate a soccer ball and this never crossed my mind. This knowledge seems pretty necessary to making accurate free kick shots.

[FirstLast-frhb]

Very well presented, your partner is quite clear headed and clearly spoken as well!

[sabymondal]

I recently started playing tennis, and i was wondering about the effect of topspin on trajectory.. Exactly what I thought! Thanks a lot !!

[vishank]

That paper cylinder demonstration is fantastic!

[ayoolumoroti]

Roberto Carlos free-kick = Magnus Force

[VincentParbelle]

Hi! The experience with the paper cylinder just baffled my students. We compared the cylinder's motion with that of a plastic tube of exactly the same size (by rolling the paper over the plastic tube in the first place).

Thanks for these inspiring videos with Rod Cross!

Btw, 2 small misprints in your introduction text:
experience -> experiences
ealier -> earlier

[garvitsharma]

The Magnus study that in 11th grade as a part of fluid dynamics here in india