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PSA712 Biomechanics > Rotation in Sport > Flashcards

Rotation in Sport Flashcards

1
Q

Motor control is defined as what?

A

The study of how movement is controlled.

The ability to regulate or direct the mechanisms essential to movement.

Regulation/maintenance of a function or action.

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2
Q

What 3 aspects of sport science does motor control involve?

A

Physiology
Biomechanics
Psychology

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3
Q

Reaction time occurs during the processing stages of a reaction. What 3 steps take place during reaction time?

A

Stimulus identification.
Response selection.
Response programming.

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4
Q

When does a somersault speed up?

A

When the shape of an individual changes from straight to tucked.

Speed of rotation increases.

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5
Q

What equation is used to work out angular momentum?

A

Angular momentum = moment of inertia x angular velocity

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6
Q

Define angular momentum.

A

A measure of the quantity of rotation of a system of matter.

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7
Q

What is the definition of inertia?

A

The resistance of a body to change its state of angular motion?

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8
Q

Inertia has 3 principle axis: Frontal, Lateral and Longitudinal. Rank them from smallest to largest when referring to the moments about the axis.

A
  1. Longitudinal
  2. Lateral
  3. Frontal
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9
Q

What is the equation to calculate inertia for a point mass?

A

Inertia = md^2

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10
Q

What is the equation to calculate the inertia for a body/real mass?

A

Inertia = Σ(md2) kg/m^2

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11
Q

State the equation used to calculate angular velocity?

A

Angular Velocity = angular displacement / time

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12
Q

What units is angular velocity measured in?

A
  • Degrees per second
  • Revolutions per second
  • Radians per second
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13
Q

What is the mechanical principle in operation for a somersault?

A

Angular momentum is constant in flight.

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14
Q

What two components must balance out, in order for momentum to remain constant?

A

Inertia and angular velocity.

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15
Q

If an athlete moves into a tucked position, angular velocity increases, what happens to inertia?

A

Decreases.

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16
Q

State the equation used to show angular momentum is conserved and constant.

A

Isωs = Itωt (s = straight, t = tucked)

17
Q

The movement of an individuals arms will do what during a somersault?

A

Cause the body to move in the opposite direction to the arms.
This ensures angular momentum = 0 as it is conserved.

18
Q

During a somersault, what movement decreases moments of inertia?

A

Tucking.

19
Q

How is a somersault produced during take-off?

Refer to CoM.

A
  1. Force acting through CoM doesn’t cause trampolinist to rotate.
  2. Leaning forward causes the force from the trampoline bed to act just behind the CoM (some horizontal force and trampolinist rotates).
  3. As the bed recoils, trampolinist flexes at the hip and the force acts behind the CoM - increases angular momentum.
20
Q

State how Newton’s law and angular momentum relate.

A

The rate of change of angular momentum of a body is proportional to the torque causing it and takes place only in the direction in which the torque acts.

21
Q

What two equations can be used to calculate torque?

A

Torque = moment of inertia x angular acceleration

Torque = force x distance

22
Q

How do long jumpers cope with forward somersault momentum during flight?

A

Arms and legs are circled forwards to prevent the body from rotating forwards (conservation of momentum = 0).

23
Q

Why do high jumpers use a curved approach?

A

To produce somersault rotation.

24
Q

The run-up curve tightens as a high jumper gets closer to the bar. Why is this?

A

Throws the athlete to the side which creates the somersault rotation they need to clear the bar.

25
Q

What equation is used to calculate rotational energy?

A

Rotational energy = 1/2 angular momentum x angular velocity

26
Q

State two forms of energy in which rotational energy can be lost as an athlete rotates around the parallel bars?

A

Heat and friction.

27
Q

How do gymnasts accurately time releasing the bar?

A

Use a technique that makes timing less critical.

28
Q

What equation can be used to calculate a gymnasts release window off the parallel bars?

A

Release window = Last time can release successfully - First time can release successfully

29
Q

What are the two ways twist can be produced?

A
  1. Contact twist

2. Arial twist

30
Q

Describe contact twist.

A

Must be in contact with something (e.g. floor), feet do not move, floor provides a torque in opposite direction.

31
Q

The hula action initiates what type of twist?

A

Arial

32
Q

What 2 ways can twist be initiated during a somersault?

A

Production of tilt using asymmetrical arms.

Production of tilt using asymmetrical hips.

33
Q

How do gymnasts control unstable movements?

A

By making corrective arm movements in flight?

PSA712 Biomechanics (8 decks)

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