It is in badminton that we observe the fastest sports balls: Malaysian Tan Boon Heong completed the record smash and hit the steering wheel at 137 m/s (493 km/h!).
If we look at the speed scale above, it is almost 2 times more than the record in tennis (73 m/s), 4 times more than in volleyball (37 m/s) and 8 times more than in handball (15 m/s). However, we cannot really say that handball players are weaker than badminton players: Karabatic is 1.95m and 102kg, against 1.81m and 75 kg for Heong.
To understand this ranking of the fastest sports, you have to understand how speed is transmitted to the ball.
Throw vs. to hit
In some sports like handball, the ball is thrown. We observe on the chronophotography of a shot below that it leaves at the speed of the hand when releasing (the length of the blue line is equal to the length of the red line).
On the other hand, when the ball is hit, as in volleyball or tennis (chronophotograph on the right), its speed is twice that of the racket. By hitting rather than throwing, we already gain a factor of 2!
This is only true if there is not (too much) energy dissipation on impact, and if the ball is lighter than the object hitting it. Otherwise, the ball/impactor velocity ratio is less than two. If the ball is heavy (handball 450g, basketball 650g, petanque 700g, weight 7.26kg), you don’t gain much by hitting it, except getting hurt. So we launch! These are the sports where the ball speeds are the lowest (at the bottom of the scale in the diagram at the beginning).
Chronophotograph of a handball shot (left, LadHyX) and a tennis serve (right, HEEdgerton) The blue line represents the distance traveled by the hand/racket between two flashes (i.e. 0.04 seconds) and the red, the distance traveled by the ball during the same time.
How to increase typing speed?
Since everything comes from the speed of the throwing object (hand, foot, racquet…), it must be maximized to achieve records. There are several ways to do this:
- increase arm length with a racket
- use the joints
- use a bungee racket
The speed of the hand is equal to the length of the arm multiplied by its speed of rotation around the shoulder. To increase this speed, one can increase the length of the arm with a racket. If the racket is the same length as the arm, we again gain a factor of 2 (which allows us to
move from the volleyball record to the tennis record)!
But you only gain this factor 2 if you are able to rotate the whole thing (arm + racket) at the same speed as the arm alone. This is what the joints are for: for a fixed effort of the muscles, it is easier to rotate an articulated arm than a rigid arm of the same length. And this is all the more true as the articulated segments are increasingly light.
Flexible vs rigide
This is the case for the leg and the arm (an 80kg person has a thigh of 11kg, a calf of 3.4kg and a foot of 1.1kg, an arm of 2.2kg, a forearm of 1, 3kg and a hand of 500g). And the rackets are all lighter than your hand (280g in tennis and 80g in badminton). The last point to understand is the factor 2 between the badminton record and the tennis record. Indeed, in these two sports, the ball is hit, and with a racquet of the same size.
The difference comes from the fact that the racket in badminton is flexible, while it is rigid in tennis. During a smash, the handle of the badminton racket undergoes such an acceleration (340 m/s^2=4*g) that the shaft twists and the head of the racket remains behind, as can be seen on the timeline of the smash below.
This stores elastic energy in the shaft (as if compressing a spring). Then, when the acceleration decreases, the shaft unfolds and restores the stored energy, the racquet head comes back violently forward. If the impact with the shuttle takes place at the moment when the speed of the racket is maximum, we can still gain a factor of 2 on the speed of the racket head. Playing on the elasticity is another way to increase the speed of the racquet. This effect is also used in hockey for the “slap-shot”: the player scrapes the stick on the ice to twist it, and uses the elastic whip to hit the puck with greater speed.
Shooting in ice hockey “Slapshot”: the player twists the stick on the ice to use its elasticity and hit the puck (at left). Shape of the badminton racket at different times during a badminton smash (right, LadHyX)
The secret of the speed record is therefore to hit the ball (x2), to use a racket and joints (x2) and the elasticity of the racket (x2). In the end, the speed of the “impactor” can therefore be multiplied by 8, which makes it possible to go from 15 m/s to 120 m/s as observed (roughly) on the speed scale.
