# Presentation: 130111

## Understanding and Misunderstanding the Physics of Sports;or“Where Do World Records in Track and Field Come From?”

- Cliff Frohlich
- Institute for Geophysics
- University of Texas at Austin

## I. Why am I here? — a disclaimer

- II. What causes sudden, discrete increases in field event records?
- III. Should discus be thrown with or against the wind?
- IV. What will the women’s pole vault record be in 2010?
- V. Is innovation in equipment and technique considered desirable?
- 	[broad jump, javelin, shot put, high jump]
- VI. Where can you publish sports physics?
- 	— the dilemma for the armchair scientist

## I. Why am I here? — a disclaimer

- 	1967 - 2nd place in springboard diving,
- 	   Midwest Conference Swim Meet (Div. III)
- 	1967 - completed first college physics course,
- 	   text: Halliday & Resnick
- 	1976 - Ph. D., physics, Cornell University,
- 	  married to assistant professor, unemployed

## II. What causes sudden, discrete changes in field event records?

- 	• Outstanding individuals, extraordinary sacrifices (training),
- 	   motivation, “heart”
- 		$$$ - money & coaching
- 	• Innovation, loopholes in the rules,
- 		physics

- Men’s Olympic pole vault

## III. Should discus be thrown with or against the wind?

- 	July 1977			July 1981			May 1976
- T&FN: 			**They Call the Wind Wonderful**
- 	When he awoke on the morning of the California relays, Ben Plucknett recalls, “I had to keep telling myself to stay calm.  The wind got me all excited.”  The breeze was whistling through Modest around 25 mph–and to any discus thrower who has ever competed in the Cal Relays event, staged as it is with the wind blowing in from the most helpful quarter, this is plenty cause for excitement...

## • Discus mass and cross section

- • Discus mass and cross section
-      fixed by rules ~1900
- • Forces for F = Ma calculation:
-      gravity - Mg downward
-      drag - opposite VREL
-      lift - normal to VREL
- • FD = 1/2 CD AIRA VREL2
-    FL = 1/2 CL AIR A VREL2
- • Drag CD and lift CL depend on angle
-      between VREL and plane of disc

- Frohlich, C. Aerodynamic effects on discus flight, *Amer. J. Phys.,49*,  1125-1132, 1981

## Slide 7

## Slide 8

## Conclusions:

- with
- wind

- against
- wind

- • Against-wind throws further
-     until about 20 m/s (40 mph)
- • Against-wind strategy:
-   - release angle ~ 15°+inclination
-   - lower inclination as wind increases,
-      disc initially knifes into wind,
-      then lift from below extends air time
- • With-wind strategy: if VW > 10 m/s
-    - throw it as high as possible,
-    - let wind catch flat side of disc
-        like a sail
- • QUESTION:
-    - Are high winds (against) always
-        better?  Or, is there an optimum
-        against-wind speed?

##          DUCK!

- Are higher winds better?
- • Higher winds against allow smaller
-     allowances for error, thus
-      favoring “expert” throwers
- • Very high winds (~ 75 m/s):
-     FD = 1/2 CD AIRA VREL2
-       Even for minimum-drag
-      CD of 0.1, wind stops forward
-      motion of disc before it reaches
-      50 m or so.
- • Very high-wind strategy:
-          **DUCK!**

- Release parameters producing throws
- within 1 meter of optimum [V0 = 25m/s]

## Conclusion:

- •  In any wind in which a competition could conceivably
-      be held (VWIND < 20 m/sec)  it is advantageous for expert
-      throwers to throw against the wind
- • Under hurricane-force conditions, it is advantageous to throw
-     with the wind.

##   Stacy Dragila: 4.81 meters	     Sergey Bubka: 6.14 meters

- 	women			    men
-   Stacy Dragila: 4.81 meters	     Sergey Bubka: 6.14 meters

- April 2001			May 2001			March 1984

## Slide 13

## Slide 14

##          Assume: hCM = 1.1 meter for Men; 

-   Kinetic energy of runup converted to
- 	gravitational potential energy

-          Assume: hCM = 1.1 meter for Men;
- 	             hCM = 1.0 meter for Women
-    How good is this model?

- January 1992

- January 1989

## Men’s Olympic 100 Meters

- Men’s Olympic Pole Vault

- Bamboo and
- Metal Poles

- Fiberglass and
- Plastic Poles

## Men’s Olympic

- Women’s world record pole vault

-   pole vault

- Pot. En. = 100% Men’s Olympic 100m

- 95%

## Pot. En. = 100%Women’s Olympic 100m

- 95%

- Women’s world record pole vault

## Conclusion: 

- 1. If we adjust pole vault performance to account for running speed,
-     women are approaching heights that are “as good as” men achieve.
- 2. However, to equal the performance of men, the women’s world
-     record will have to get about 40 cm higher than at present.
- Sergey Bubka: 6.14 meters
- 	hCM = 1.1 m; V100%Men’s Olympic  implies 6.34 meters
- 	difference: 0.2 meters
- Stacey Dragila: 4.81 meters
- 	hCM = 1.0 m; V100%Women’s Olympic implies 5.41 meters
- 	difference: 0.6 meters

## Is the “Simplified Pole Vault Model” any good?

- Ekvad, M. and B. Lundberg. Simulation of ‘smart’ pole vaulting, *J. Biomechanics, 28*,
- 	1079-1090, 1995.
- Ekvad, M. and B. Lundberg. Influence of pole length and stiffness on the energy
- 	conversion in pole-vaulting, *J. Biomechanics, 30*, 259-264, 1997.
- Ekvad and Lundberg perform finite element modeling for two models of the pole vault:
-    • Vaulter is a passive, point mass at very end of pole
- 	Conclusion: for optimum height case, height achieved corresponds to 87%
- 	   of kinetic energy
-    • Vaulter made up of 7 elements that apply muscle torques according to a given strategy
- 	Conclusion: for optimum height case, height achieved corresponds to 127%
- 	  of kinetic energy.

## short

- pole

- long
- pole

- low stiffness			high stiffness

## long pole, optimal stiffness		optimal length, optimal stiffness

- long pole, optimal stiffness		optimal length, optimal stiffness

- Conclusion: Vaulter most choose pole with appropriate length and stiffness

## V. Is innovation in equipment and technique a considered desirable?

- 	broad jump - 1973: somersault long jump

- Ecker, T.  *Track and Field Dynamics*, 1974: “Research in the United States and in Scandinavia has shown that the somersault long jump technique is dynamically superior to any other technique being used at this writing.  Someday in the future it should be good for jumps of 30 feet (9.15 m) or more.”

## Slide 24

## Slide 25

## Long jump physics and facts:

-   • Current world record is 8.95 meters (Mike Powell)

-   November 1991		         March 1992

## Long jump physics and facts:

- • World-class long-jumpers are world-class sprinters

## Long jump physics and facts:

- • Optimum jump technique is _not_ simple matter of
- 	projecting body at ‘best’ angle of 45°
-      - _If_ jumpers could do this:
- 	would achieve 10.47 meters and
- 	cm would clear 2.55 m higher than takeoff
- 	  (making 3.55 m high-jump possible)
- Better simple long jump model:
-   • jump distance controlled by sprint speed V and
- 	height hJUMP that jumper can raise cm during jump:

- horizontal 	        time                      time
- velocity              up		down

## Men’s Olympic 100m time

- Men’s Olympic long jump distance

- Model:
- hJUMP = 1.1m;
-  hLJ=0.5m

## Women’s Olympic 100m time

- Women’s Olympic long jump distance

- Model:
- hJUMP = 0.9m;
-  hLJ=0.5m

## V. Is innovation in equipment and technology considered desirable?

-      Somersault long jump, forward takeoff allows jumper
-                        	to jump higher while maintaining velocity.
-      Answer long jump NO! Sumersault variety long jump was banned                                      		ostensibly for reasons of safety.
-      Would a quote roundoff long jump have allowed athlete to
- 		achieve even greater vertical height?
-      We will never know...

## V. Is innovation in equipment and technique a considered desirable?

- 	shot put -
- 		spin vs glide
- 		drugs vs no drugs

- World record

- 10th best performance
-      each year

## V. Is innovation in equipment and technique a considered desirable?

- 	high jump - roll vs flop

## V. Is innovation in equipment and technique a considered desirable?

- 	The case of the javelin:

- Olympic winners’ distance:
-    javelin, hammer, discus

## Early 20th century javelin specifications fixed mass, but did not fix

- 	implement cross section or mass distribution
- 1953 - Franklin “Bud” Held invents hollow javelin; increased surface
- 	area made it more aerodynamic
- 1954 - Held invents hollow metal variant.  Markets same.
- 1966 - “Spaniard Felix Erausquin threw over 100 meters using a
- 	rotational technique, which was banned by the IAAF as
- 	too dangerous.”
- 1984 - Uwe Hohn throws javelin 104.8 meters (344 feet)
- 1985 - IAAF redesigns javelin; intent is to limit distance to 90 meters

## V. Is innovation in equipment and technique considered desirable?

- 	broad jump technique - 	NO - somersault is bad
- 	shot put technique - 	YES - spin or glide is good
- 	shot put ‘training’ (drugs)	NO - _detectable_ drugs bad
- 	high jump technique	YES - flop OK
- 	javelin equipment		YES - 1960, new javelin OK
- 	javelin equipment		NO - 1986, not OK
- 	javelin technique		NO - 1966, discus spin is bad
- 	pole vault equipment	YES - 1960, plastic pole is good
- Note: not a clear message about danger, innovation
- What will cause future discrete increases (changes) in track and field
- 	records?
- 	“tuned” track surfaces?
- 	surgery to improve performance?
- 	selective breeding?

## VII. Where can you publish sports physics? 

- 	— the dilemma for the armchair scientist
- _The Crying of Lot 49_ (by Thomas Pyncheon):
- In this classic novel of the 60’s, there are two kinds of people in society:
- 	• those who are aware of and use the underground postal system
-      	  which has been in place for centuries;
- 	• those who are completely unaware of the underground system,
-      	  and only use the regular, government-sponsored post.
- There are three kinds of people who seriously analyze sport:
- 	• an “underground” of individuals who follow individual sports
-    	 passionately and intelligently, but would never think of
- 	 publishing in some fancy journal;
- 	• coaches and self-styled “experts” who often publish in
- 	  journals designed for the serious enthusiast, but _not_ for scientists
- 	• individuals with scientific training who occasionally publish sports
-    	articles in various biomechanics or ‘cultural’ physics journals, which
-    	often aren’t appropriate for serious analysis

## Where can you publish sports analysis that is physics or mechanics?

- • *American Journal of Physics*
-   - “cultural” physics;  will consider articles that present (over) simplified models of sport,
- 	even if they are not particularly new
- • *Journal of Biomechanics*
-   - most articles have a decidedly medical flavor (hydrodynamics of blood, etc.)
- • *Journal of Applied Biomechanics*
- • *Journal of Sport Sciences*
-   - articles often focus on analysis of photographic observations of performance;
-   - sometimes conclusion of articles seems obvious to a physicist
- 	[e. g., optimum release angle for shot put is ~ 45°]
- • Journals for coaches and enthusiasts (beware of their reviewers)
-   - *Bowling this Month*
-   - *Track Coach* (formerly Track Technique)

## Problem: where to publish sports analysis that isn’t physics or mechanics? 

**Problem: where to publish sports analysis that isn’t physics or mechanics?**

- Frohlich, C. and G. Scott.  Where spectators sit to catch  baseballs, _Baseball Res. J., 10_, 132-138 1981