Biomechanics SUNY Brockport (Danny Too) Exam 1

Physiological Kinesiology

is the study of the response of the systems of the body to the stress of exercise

Psychological Kinesiology

is the study if these topics applied to human movements

Philosophical Kinesiology

is the study of the value of movement to an individual or in a society

Sociological Kinesiology

is the study of human interaction during the course of moving,playing, or participating in an activity or sport

Mechanical Kinesiology

is the study of human movement using Newton's Laws

Statics

is the study of mechanical properties of objects that are in equalibrium (not moving)

(e.g foot contact during walking, compression of the meniscus of the knee)

Statics and Forces

Stress force- the application of force to an object, which causes Strain- the development of internal forces

Kinematics

the description of the motion of an object,

displacement,

velocity,

and acceleration

Dynamics

is the study of the mechanical properties of objects that ARE IN MOTION such that relative motion occurs between an object and the environment

Internal forces

can cause changes in body shape

can change the position of the center of mass WITHIN THE BODY

(e.g muscles)

External Forces

Friction,Gravity,Ground Reaction Forces

Polar Coordinate System

Scalar Quantities

quantities that have magnitude only (speed, temp, and mass)

Vector Quantities

have magnitude and direction (displacement, velocity, force, and contact forces)

Graphical Vector Properties

Vector Quantity Representing Gravity in a global reference system

(0,9.8m/s^2))

Stabilizing Component of Muscle Force

-acts parallel to the segment being moved by the muscle

-can be directed towards the joint

-can be directed away from the joint

Angle of Pull is <90 degrees

the direction of the the SC is always towards the joint and exerts a compressive force at the joint increasing stability

Angle of Pull is >90 degrees

the direction of the SC is always away from the joint, and exerts a dislocating force at the joint which would tend to decrease stability

Angle of Pull <45 degrees

the SC is always greater than the RC

Angle of Pull between 45 and 135 degrees

the RC is greater than the SC

Angle of Pull greater than 135 degrees

the SC is greater than the RC

At exactly 45 and 135 degrees

SC and RC are equal, and there is no dominant role of the muscle as it does both functions equally well

At exactly 90 degrees

there is no SC

Factors Affecting Friction

-the type of material of the surfaces in contact

-the smoothness or irregularities of the surfaces

-the velocity of the movement

-the normal force (holding/pressing the two surfaces together)

Friction

is a force that opposes the sliding of one object over another, and opposes the rolling of one object over another

In a Local Reference System, friction can only act...

along the x-axis

In a Global Reference System, friction can only act...

at any angle between the x and y axis

In GRS friction for a magnet on a vertical metal surface will act...

along the +y-axis

In a LRS, friction for an object on a vertical surface will act...

along the -x-axis

Affects Frictional Force for an Object on a Horizontal Surface

-normal force

-perpendicular force

-the weight of the object

What affects frictional forces between two surfaces?

-velocity of movement

-smoothness/irregularities of the surface

-magnitude of the force holding the surfaces together

-type of material

Coefficient of Friction

1.0>(u)>0

Coefficient of Friction for (starting, stopping, static, and non-moving)

(u=1.0)

Coefficient of Friction for (moving sliding, dynamic, and kinetic)

(u)<1.0

Coefficient of Friction for (rolling)

(0.1>u>0.0001)

The Calculation of the Coefficient of Friction

(u)=(FFR)/(FN)

When pulling an object...

friction decreases because the normal force has decreased

When pushing an object with arms parallel to the ground...

normal force will remain unchanged in the object being pushed and the person doing the pushing

Buoyancy

-is created as an object is immersed in a fluid

-is equal to the weight of the fluid displaced by the object

-always acts vertically upwards in a global reference system

-always acts on the opposite direction of gravity

If specific gravity of object is >1.00 than...

object will sink

If specific gravity of object is less than or equal to 1.00 than...

object will float

Stable Floating Position

-center of buoyancy located at or above the center of gravity

Unstable Floating Position

-center of buoyancy located below the center of gravity

Drag Force only occurs when....

there is movement

Static Fluid Force exists when....

an object is floating in water

If the two systems are moving in the same direction, then the relative velocity is found by...

taking the difference between them <--, <---- = subtract adding both <---,----> = +

(same for Drag Force)

If the two systems are moving in the opposite direction, then the relative velocity is found by...

adding both <---,----> = +

(same for Drag Force)

Drag Force in a GRS

If vector is (5,45 degrees) then drag force is (5,225 degrees)

its opposite

for Drag Force as velocity doubles...

drag force is quadrupled

Surface Drag is also called...

viscous drag or skin friciton

The Mathematical Calculation of Drag Force includes

-the coefficient of drag

-the cross-sectional area

-fluid density

-fluid velocity

Form Drag is also known as..

pressure drag or profile drag

Factors Affecting Form Drag are..

-The shape of the body

-the CSA of the object, that is PERPENDICULAR to the direction of motion

-the density of fluid

-the relative velocity

Factors Affecting Surface Drag

-the smoothness of the object

-the CSA of the object, that is PARALLEL to the direction of motion

-the density of the fluid

-the relative velocity

Lift Force will always...

act perpendicular to drag force and the oncoming fluid flow

A tennis ball hit with topspin, moving forward and upward will experience a Magnus effect that is....

downward and forward

When a baseball is moving straight up over home plate (perpendicular to the ground) the Magnus effect will cause the ball to move towards the back stop