Chapter 12 - Rotation Flashcards
What are the names of the three rotational axes (give examples)?
Longitudinal (spins, turns)
Transverse (rolls, bar circles)
Anterior/posterior axis (cartwheels)
What are rotations caused by?
Rotations are caused by off-centre forces. Off-centre forces do not pass through the centre of mass.
What is displacement?
Displacement is when something is moved (pushed perhaps) and a force is passing through the centre of mass directly, linear motion occurs.
What is a force couple?
When two off-centre forces work together and help to rotate the body in different ways.
Where is the longitudinal axis?
head to toe (imagine a pole through head to toe)
What is the Transverse axis?
hip to hip
What is the Anterior/ Posterior axis?
front to back
“for every action there is an _____”?
equal and opposite reaction
The further off centre the more ___, less ___
more rotation and less displacement
What is altering rotation?
distribution around the centre of mass
What is inertia?
object at rest
How do you mechanically generate all rotations?
- swinging the body along the axis
- stationary with offcentre force ( the further away the more rotation)
- force couple
Which axis do we swing about?
external axis
In the descending part of a swing, is gravity good or bad?
it is good because it increases rotation
where is the COM in the descending part of a swing?
the com is farther from the bar, do shoulder elevation
Where do you want the COM in the ascending part of a swing?
as close to the bar as possible
What muscle state is in the descending part of a swing?
eccentric (straight arms and legs)
What muscle state is in the ascending part of a swing?
concentric (bent arms and legs)
How do you go higher in the ascending part of a swing?
distribute body mass closer to the axis its working on
Is gravity good or bad in the ascending part of a swing?
it is bad, negative off center force
What will friction cause during rotation? How do you stop it?
less rotation and sore hands therefore hook not squeeze.
What is the difference between hook and squeeze in a swing?
hook: less surface therefore less friction, cant swing as far, not as slow
squeeze: more surface area, more friction, swing longer, hang on longer, slow
when do you regrasp in a swing?
on the backswing
what is a key fundamental for swinging?
hangs
what is torque?
force times lever arm
how do you get a shorter radius for a closer COM
bend at shoulders
