Chapter 12 - Rotation

Question 1

What are the names of the three rotational axes (give examples)?

Answer 1

Longitudinal (spins, turns)
Transverse (rolls, bar circles)
Anterior/posterior axis (cartwheels)

Question 2

What are rotations caused by?

Answer 2

Rotations are caused by off-centre forces. Off-centre forces do not pass through the centre of mass.

Question 3

What is displacement?

Answer 3

Displacement is when something is moved (pushed perhaps) and a force is passing through the centre of mass directly, linear motion occurs.

Question 4

What is a force couple?

Answer 4

When two off-centre forces work together and help to rotate the body in different ways.

Question 5

Where is the longitudinal axis?

Answer 5

head to toe (imagine a pole through head to toe)

Question 6

What is the Transverse axis?

Answer 6

hip to hip

Question 7

What is the Anterior/ Posterior axis?

Answer 7

front to back

Question 8

“for every action there is an _____”?

Answer 8

equal and opposite reaction

Question 9

The further off centre the more ___, less ___

Answer 9

more rotation and less displacement

Question 10

What is altering rotation?

Answer 10

distribution around the centre of mass

Question 11

What is inertia?

Answer 11

object at rest

Question 12

How do you mechanically generate all rotations?

Answer 12

• swinging the body along the axis
• stationary with offcentre force ( the further away the more rotation)
• force couple

Question 13

Which axis do we swing about?

Answer 13

external axis

Question 14

In the descending part of a swing, is gravity good or bad?

Answer 14

it is good because it increases rotation

Question 15

where is the COM in the descending part of a swing?

Answer 15

the com is farther from the bar, do shoulder elevation

Question 16

Where do you want the COM in the ascending part of a swing?

Answer 16

as close to the bar as possible

Question 17

What muscle state is in the descending part of a swing?

Answer 17

eccentric (straight arms and legs)

Question 18

What muscle state is in the ascending part of a swing?

Answer 18

concentric (bent arms and legs)

Question 19

How do you go higher in the ascending part of a swing?

Answer 19

distribute body mass closer to the axis its working on

Question 20

Is gravity good or bad in the ascending part of a swing?

Answer 20

it is bad, negative off center force

Question 21

What will friction cause during rotation? How do you stop it?

Answer 21

less rotation and sore hands therefore hook not squeeze.

Question 22

What is the difference between hook and squeeze in a swing?

Answer 22

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

Question 23

when do you regrasp in a swing?

Answer 23

on the backswing

Question 24

what is a key fundamental for swinging?

Answer 24

hangs

Question 25

what is torque?

Answer 25

force times lever arm

Question 26

how do you get a shorter radius for a closer COM

Answer 26

bend at shoulders