Sports Biomechanics- Quiz 3

This set of flashcards covers key concepts from the study of angular kinetics and stability, including definitions of terms and important principles.

Angular Kinetics

The study of rotation and the forces involved in rotation.

Center of Gravity (COG)

The balance point of the body or object, dependent on body composition and position of limbs.

Angular Momentum (H)

Defined as H = Iw, where H is angular momentum, I is moment of inertia, and w is angular velocity.

Conservation of Angular Momentum

Angular momentum remains constant if no external torque acts on the body.

Stability

Resistance to disturbance; the ability to maintain control over the base of support.

Base of Support (BOS)

The area beneath an object; a larger BOS increases stability.

Line of Gravity (LOG)

A vertical line from the center of gravity that must remain within the base of support for stability.

Moment of Inertia

A measure of an object's resistance to angular acceleration, dependent on mass distribution relative to the axis of rotation.

Centripetal Force

The force that keeps an object moving in a circular path, directed towards the center of rotation.

Centrifugal Force

The apparent force that pushes an object outward when it is in a rotating reference frame.

What is angular kinetics?

study of rotation and the forces involved in rotation

What does rotation occur around?

axis of rotation

Two types of axes?

external axis and internal axis (center of gravity)

What can gravity do to rotation?

initiate or limit rotation

What happens to velocity from a higher drop?

final velocity increasesW

Why doesn’t a parachutist accelerate forever?

reaches terminal velocity due to air resistance

What is COG (center of gravity)?

balance point of the body/object

Does COG always stay in one place?

no, it moves with body position

Where is COG typically locates?

around belly button

Who has a lower COG?

females

How can you change COG?

move limbs

Formula for angular momentum?

H=Iω

What does angular momentum depend on?

mass, distribution of mass, angular velocity

Moment of Inertia formula

I=mk²

Which matters more: mass or radius? (in terms of moment of inertia)

radius (k)

3 ways to increase angular momentum

increase mass, increase angular velocity, increase radius from axis of rotation (increase distance from axis)

What happens to angular momentum in flight?

it stays constant

If moment of inertia increases, what happens to speed?

decreases

Skater pulls arms in → what happens?

spins faster

How do cats land on their feet?

rotate body segments in opposite directions

What is stability?

resistance to disturbance

What is balance?

control of body over base of support

What increases stability?

larger BOS (base of support)

Where must LOG (line of gravity) be for stability?

inside BOS

When does instability occur?

LOG moves outside BOS

List 4 factors for increasing stability

increase BOS, lower COG, increase mass, keep LOG inside BOS

Angular kinetics is the study of:

rotation and forces

Gravity can:

initiate or limit rotation

The center of gravity is:

the balance point

Angular momentum formula:

H = Iω

If moment of inertia increases:

speed decreases

Pulling arms inward while spinning:

speeds up spin

Which has more influence on inertia?

radius

Stability increases when:

BOS increases

Instability occurs when:

LOG outside BOS

Cats land on feet because:

they rotate body segments

Angular kinetics studies ________ and ______.

rotation, forces

Gravity causes _______ acceleration.

downward

COG stands for ______ __ _______.

center of gravity

H = __

Iω

I= ___

mk²

If I increases, ω _________.

decreases

Stability = resistance to ___________.

disturbance

LOG must stay inside ___.

BOS (the Base of Support)

Bigger BOS = ____ stability

more

Lower COG = ____ stability

more

If a skate extends arms outward, what happens?

moment of inertia increases → spin slows

Why do sprinters lean forward?

to reduce stability and increase speed

Why do wrestlers lower their body?

to lower COG and increase stability

Why is radius more important than mass?

because it it squares in I=mk²

Why to divers tuck?

reduce moment of inertia → spin faster