Biomechanica Initiator ski

Dia 1
Biomechanica
Initiator ski
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Dia 2
Basisbegrippen
• Kracht
→ grootte
→ richting
→ zin
→ aangrijpingspunt
F = 300N
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Dia 3
Wetten van Newton
1 ste wet = traagheidswet
Elk lichaam wil zijn toestand van rust of
beweging behouden.
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Dia 4
Wetten van Newton
2de wet : F = m x a
→ F = kracht in Newton
→ m = massa in kg
→ a = versnelling in m/s2
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Dia 5
Wetten van Newton
3de Wet: Actie = Reactie
Als lichaam A een kracht uitoefent op
lichaam B
→ lichaam B oefent een even grote maar
tegengestelde kracht uit op lichaam A.
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Dia 6
Evenwicht
Bewegingsvlakken
• Frontaal = breedtevlak
•Sagitaal = dieptevlak
•Transversaal = horizontaal
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Dia 7
Evenwicht
Statisch Evenwicht
Projectie van het
LZP valt binnen het
steunvlak.
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Dia 8
Evenwicht
Dynamisch Evenwicht
De werklijn van FR
valt binnen het
steunvlak.
FR
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Dia 9
Uitwendige krachten
Zwaartekracht
→ FG = m x g (g = 9,81 m/s2)
→ grijpt aan in LZP
→ verticaal naar beneden
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Dia 10
Uitwendige krachten
Zwaartekracht
Afglijdende component
Normale component
Zwaartekracht
Hoe steiler de helling, hoe groter FA !
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Dia 11
Uitwendige krachten
Zwaartekracht
→ Werkt de inzet van de bocht tegen
(lagere niveaus)
→ zorgt voor een versnelling
→ bevordert het wegslippen van de ski’s
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Dia 12
Uitwendige krachten
Weerstand van de sneeuw op de ski’s
Afhankelijk van:
→ inkantingsgraad
→ hellingsgraad
→sneeuwkwaliteit
→toestand van de ski’s
→skipositie
→vorm van het terrein
→…..
Werkt
steeds de
bewegings
richting
tegen!
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Dia 13
Uitwendige krachten
Weerstand van de sneeuw op de ski’s
1. Ski’s vlak op de sneeuw
FW afhankelijk van:
→ FG
→ hellingsgraad
→ skioppervlak
→ toestand van de sneeuw
→ toestand van de ski
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Dia 14
Uitwendige krachten
Weerstand van de sneeuw op de ski’s
2. Stilstand - ski’s ingekant
FW loodrecht op lengte-as van de ski’s
Angulatie: hoek tussen bovenste en
onderste ledematen
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Dia 15
Uitwendige krachten
Weerstand van de sneeuw op de ski’s
3. In beweging – tijdens een bocht
Inkantingsgraad bepaalt FWR
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Dia 16
Uitwendige krachten
Centrifugale kracht
→ schijnkracht die ons uit de bocht lijkt te trekken
→ merkbaar omdat we van richting veranderen
→ t.g.v. de centripetaalkracht FCP
→ vanuit het centrum van de bocht naar buiten toe
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Dia 17
Uitwendige krachten
Centrifugale kracht
FCf
FCp
→ neemt kwadratisch toe met de snelheid
→ neemt toe als straal van de bocht kleiner wordt
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Dia 18
Uitwendige krachten
Centrifugale kracht
FC = m x v2
R
m = massa
v = snelheid
R = straal van de bocht
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Dia 19
Uitwendige krachten
• Centrifugale kracht
De skiër zal in eerste instantie inclineren om in
evenwicht te blijven.
Inclinatie = hoek die de
skiër maakt met de
verticale
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Dia 20
Uitwendige krachten
Centrifugale kracht
Bij hogere snelheden zal ook angulatie optreden
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Dia 21
Uitwendige krachten
Luchtweerstand
Werkt steeds remmend en is afhankelijk
van:
→ houding van de skiër
→ snelheid (kwadratisch)
→ oppervlakte van de grootste doorsnede
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Dia 22
Uitwendige krachten
Reactiekrachten van het terrein
Ontstaan door:
→ oneffenheden in het terrein
(bijv. bulten, terreinovergang)
→ door interne actiekracht van de skiër
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Dia 23
Inwendige krachten
Uitgeoefend door de skiër zelf
Agerend om een bepaalde
drukverandering ter hoogte van de ski’s uit
te lokken
Bijv. redressement orienté
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Dia 24
Inwendige krachten
Uitgeoefend door de skiër zelf
Reagerend op de op hem inwerkende
krachten.
Bijv. opvangen van een drukreactie
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Dia 25
Einde
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