S2- Lab 3- Understanding Rotational Motion Flashcards
When looking at a problem in long jump we need to understand the principle of “conservation of angular momentum”, what is this?
“if no external torque (turning force) acts on the body, angular momentum is constant”
Angular momentum= angular velocity x moment of inertia
Problem: during the take off of long jump, some linear momentum becomes angular momentum, when landing jumpers need their heels as far in front of their hips as possible which is hard if they have rotated.
Question: what can they do during flight to reduce and minimise the forward rotation?
Raise their arms above their head to manipulate and change their moment of inertia
Problem: during the take off of long jump, some linear momentum becomes angular momentum, when landing jumpers need their heels as far in front of their hips as possible which is hard if they have rotated.
Question: what can they do during flight to reduce and minimise the forward rotation?
Raise their arms above their head to manipulate and change their moment of inertia
A change in moment of inertia will allow a change in the position of the centre of mass
They could also look to counteract their forwards rotation and rotate backwards in the opposite direction- counteract MI and increase distribution
What are the benefits and disadvantages to the long jump hang technique?
-Distribution of MI- decreases AV and stops rotation
-Rotate around the saggital plane, counteracting forwards rotation
-Can slow down movement and forward rotation
NEGATIVES: they decrease their AV and therefore their overall speed when in flight
What are the benefits and disadvantages of the hitch-kick technique?
-Counteract forwards rotation
-Arms and legs rotate so overall body doesn’t feel the angular momentum at the end of jump
NEGATIVES: a more technically advanced skill that not all can access
When deciding which technique to promote to an athlete, what factors should a coach consider?
-AGE- younger will most likely go for the hang technique
-TECHNICAL COMPETENCY- harder and more advanced techniques will be for the hitch-kick
Calculation:
A long jumper achieves a flight time of 0.85s, and using. basic technique rotates 39 degrees during flight.
What is their average angular velocity throughout flight in degrees per second?
Angular Velocity= angular displacement/ time
= 39 degrees / 0.85 seconds
=46 rad/ s
Describe in depth the “Hang Technique” in long jump?
Performed by stretching out during the flight phase and holding this position until they have to transition into their landing position.
However, in doing this they need to be careful they don’t compromise their take off and complete the drive through the lead leg.
When performing, increases moment of inertia during the flight phase, which in turn (due to the conservation of AM) slows the rate of forward rotation= better landing position.
