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Def of biomechanics
study of forces and their effects on living systems

What are the goals of exercise and sport biomechanics?
 performance improvement:
 technique and training
 equipment
 injury prevention and rehabilitation:
 techniques to reduce injury
 equipment designed to reduce injury (braces)

Def of fluid mechanics?
branch of mechanics dealing with the movement of objects through fluids and gases

Important rigidbody mechanics concepts:
a) objects are perfectly rigid
b) best branch for describing and explaining movement
c) statics; rest/constant state/no acceleration
d) dynamics; objects accelerating/decelerating
e) kinematics; decription of motion
f) kinetics; forces and torques that cause changes
g) all of the above
g) all of the above are RIGIDBODY MECHANIC concepts!

Def of statics?
bonus: give an example
the mechanics of objects at rest or in a constand state of motion (no acceleration)
example: sitting, whole body can be static, or can be used just to describe a single body part (i.e. foot)

Def of dynamics?
bonus: give an example
the mechanics of objects that are accelerating or decelerating
example: start of a race

Def of kinematics?
branch of biomechanics concerned with the description of motion

Def of kinetics?
the branch of biomechanics concerned with the forces (and torques) that cause changes in motion
(explains HOW forces and torques CAUSE changes in motion)

Def of Mass?
Units?
 quantity of matter making up an object
 kilogram (kg)

Def of gravity?
Units?
 The attraction of one object to another object
 GRAVITY IS NOT A FORCE or AN ACCELERATION!
m/s ^{2 }

What is weight?
Units?
Weight is the FORCE due to gravity.
WEIGHT IS NOT MEASURED IN KG!

Def of motion?
What are the two things required for motion to occur?
Motion is a change in position

What are the 3 types of motion?
 1)linear (aka translation) (2 types of translation)
 2)angular
 3)general

What are the characteristics that make up rectilinear motion/translation?
 all points move the same distance at the same time
 ALL points move in a STRAIGHT LINE
 direction does not change
 orientation does not change
 described with 1 number/ONE DIMENSION

What are the characteristics that make up curvilinear motion/translation?
 all points move the same distance at the same time
 the PATHS followed by the points are CURVED
 DIRECTION CHANGES
 orientation does not change
 described with 2 numbers/TWO DIMENSIONS

What are the characteristics that make up angular motion?
(AKA: rotary motion, rotation)
 all points on a body move in ircles about the same fixed central line or axis
 can occure about an axis withing the body OR OUTSIDE the body
 paths are curved
 POINTS MOVE DIFFERENT DISTANCES
 orientation DOES CHANGE

What is general motion?
What are examples of general motion?
 A combo of linear AND angular motions
 EX: running and walking
 (TRUNK moves LINEARLY)
 (ARMS and LEGS move ANGULARLY)

Linear Distance Traveled (ℓ)
The length of the path traveled

Linear displacement (d)
 The straight line in a specific direction from initial position to final position.
 Displacement is a VECTOR
 IF movement is RECTILINEAR/STRIGHT LINE... then distance (ℓ) is the magnitude of displacement!
 Vectors can be resolved into components!


What is linear kinematics used to describe?
How quickely something changes its linear position

The branch of mechanics that is the best for describing & explaininghuman movement is:
A kinematicsE kinetic
B rigid body mechanics
C dynamics
D fluid mechanics
B rigid body mechanics (this multiple choice question has been scrambled)

Fluid mechanics is the study of movement of objects through:
A fluids
B both A and B
C gases
D all of the abov
E space
B both A and B (this multiple choice question has been scrambled)

Which of the following is the metric unit for weight and for force:
A pound
B kilogram
C Newton
D both B and C
E all of the above
C Newton (this multiple choice question has been scrambled)

"The mechanics of objects that are accelerating or decelerating" is thedefinition of:
A kinetics
B kinematics
C dynamics
D biomechanic
E statics
C dynamics (this multiple choice question has been scrambled)

Average velocity is calculated as:
A speed divided by the time it took to travel the distance
B displacement divided b
C displacement divided by the time it took for the displacement to occur
D distance divided by the speed used to travel the distance
C displacement divided by the time it took for the displacement to occur (this multiple choice question has been scrambled)

If you are slowing down,
A the direction of speed and acceleration are opposite
B the direction of displacement and acceleration are opposite
C both B and D
D the direction of speed and acceleration are the same
E the direction of displacement and acceleration are the same
B the direction of displacement and acceleration are opposite (this multiple choice question has been scrambled)

Gravity is:
A a weight
B all of the abov
C a force
D both B and C
E the attraction of two objects towards each other
E the attraction of two objects towards each other (this multiple choice question has been scrambled)

Which of the following are characteristics of displacement:
A magnitude
B direction
C vector
D both A and B
E all of the above
E all of the above

Which of the following statements about force is/are true:
A Force is a push or pull
B Force is a vector
C Force causes a change in motion
D both A and B
E all of the above
E all of the above

Which of the following factors influences the magnitude of a friction force?
A parallel force and coefficient of friction
B normal force and coefficient of friction
C contact area and coefficient of friction
D normal force and contact area
E parallel force and contact area
B normal force and coefficient of friction (this multiple choice question has been scrambled)

Which of the following is an external, noncontact force?
A weight
B Both A and B
C gravity
D mass
E all of the above
A weight (this multiple choice question has been scrambled)

Assuming the normal force does not change, the largest amount of friction would be generated between contact surfaces that are:
A hard and rough
B soft and smoot
C soft and rough
D hard and smooth
C soft and rough (this multiple choice question has been scrambled)

Conservation of momentum "requires" which of the following conditions?
A friction force is increa
B displacement is zero
C net internal force is d
D net external force is z
E acceleration is consta
D net external force is z (this multiple choice question has been scrambled)

What happens to momentum when an impulse acts on a system?
A momentum is increased
B momentum remains constant
C momentum is decreased
D Either A or B
E none of the above
D Either A or B (this multiple choice question has been scrambled)

ImpulseMomentum "requires" which of the following conditions?
A The net external force is zero
B The object's acceleration is zero
C The objects's velocity is constant
D There is a net external force
E There is no friction force
D There is a net external force (this multiple choice question has been scrambled)

Which of the following statements is/are true about Newton's first law of motion?
A It is the basis for ImpulseMomentum
B both A and C
C both A and B
D It is the basis for Conservation of Momentum
E It is known as the Law of Inertia
C both A and B (this multiple choice question has been scrambled)

Average Linear Speed
 Linear distance traveled divided by the time it took to travel that linear distance.
 s^{=}(ℓ)/t

Linear Velocity
RATE of motion in a SPECIFIC DIRECTION, A VECTOR QUANTITY

Average Linear Velocity
 Linear DISPLACEMENT of an object divided by time it took for displacement to occur.
 v^{} = d/t

Instantaneous velocity...
same as instantaneous speed except a direction is indicated

If motion is RECTILINEAR, the average speed is the same number as the magnitude of the average linear velocity
UNITS; m/s
Instantaneous linear SPEED is always the magnitude of instantaneous linear VELOCITY!

"ball throw up; linearly decelerates on the way up, and linearly accelerates on the way down"
what does this describe?
Linear acceleration

Mechanical def of linear acceleration
 the rate of change in linear velocity
 it is a vector quantity

AVERAGE linear acceleration equation in words
What units is AVG linear accel measured in?
change in linear velocity of an object divided by the time it took for the change to occur
a^{ }= ∆V/t = V_{f}  V_{i} /t
m/s2

A negative linear velocity indicates:
motion in the negative direction

Motion in the positive direction coupled with positive linear acceleration means:
an increase in the magnitude of velocity, therefore increasing speed

A linear velocity of zero indicates:
no motion at all

Motion in the positive direction coupled with negative linear acceleration means:
a decrease in the magnitude of velocity, therefore decreasing speed

A (nonzero) constant linear velocity means:
speed and direction remain the same

Motion in the negative direction coupled with negative linear acceleration means:
an increase in the magnitude of velocity, therefore increasing speed

Zero linear acceleration can mean:
either no motion or no change in the linear velocity of a moving object

Motion in the negative direction coupled with positive linear acceleration means:
a decrease in the magnitude of velocity, therefore decreasing speed

 acceleration can NOT be directly observed!
 the direction of motion is not necessarily the same as the direction of linear acceleration
 IF YOU ARE SPEEDING UP, YOU LINEAR ACCELERATION IS IN THE DIRECTION OF YOUR LINEAR MOTION
 IF YOU ARE SLOWING DOWN, YOU LINEAR ACCELERATION IS IN THE OPPOSITE DIRECTINO OF YOUR LINEAR MOTION

Def of a force:
 A push or pull
 Cause or change motion
 A vector: magnitude, direction, line of action, point of application.

Unit of measurement for a force?
Newtons! (N)

Tensile Force=
 pulling or strecthing force directed axially through body
 TENDON ON BONE

Compressive Forces=
pressing or squeezing force directed axially through body
BONE TO BONE

Shear forces=
force directed PERPENDICULAR to the forces directed axially through a body
TORN LIGAMENTS TENDONITIS
MOST INJURIES

Weight=
the force that causes two nontouching objects to move towards each other
W=(m)(g)

Mass=
the amount of matter that consitutes and object

Gravity is:
 Magnitude = 9.81 m/s2
 Direction= downward

External forces=
forces that act on an object as a result of its interaction with the environment (can be solid or liquid)

Normal component
force that acts PERPENDICULAR to the surfaces in contact

During running, the force that upward on the runner is the ______________ ______________.
normal component

Parallel component
force that acts parallel to the surfaces in contact.

During running, the force that opposes sliding of the shoe and the ground is the __________ ___________.
Parallel component

Friction force is a contact, external force that results from:
the interaction between the molecules of the surfaces in contact (fluid or dry)

Center of gravity=
an imaginary point in space through which the weight acts on an object
aka; the point of application of WEIGHT!

Dynamic/sliding/kinetic friction=
DRY friction between two surfaces that are moving relative to each other

The greater the normal force, the greater the ___________.
Friction

Why does greater friction develope between soft and rough surfaces?
Because the molecules can interact more easily with a greater coefficient of friction.

Linear kinetics = EXPLAINING the CAUSES of linear motion

Definition of linear kinetics=
study of forces that cause objects to linearly accelerate or decelerate (change in motion)

1st Law = Law of __________
Intertia

what does the 1st law state
 an object that is moving will continue to move in the same direction (straight line) with the same velocity/speed
 an object at rest will stay at rest
 UNLESS it is "compelled to change that state by forces impress upon it"

Linear inertia =
What is the body's linear inertia?
the quantity that RESISTS a change in an object's linear motion.
 MASS (m) represents the body's linear inertia
 THE GREATER the mass, the GREATER the resistance to change (think of small ball vs. giant ball rolling down a hill... which one is easier to stop?)

WHAT IS THE UNIT OF MEASURE for LINEAR INERTIA!?
kilogram (kg)

Linear momentum (L) =
what is the unit of measure.?
 the product of an object's linear inertia and its linear velocity
 L = (m)(V)
 the faster an object moves linearly, the more linear momentum it has
 the larger an object's mass, the more linear momentum it has
kgm/s kilogram meter per second

what is "quanity of motion" of an object? (aka)
Linear momentum; is way of QUANTIFYING the linear motion and linear inertia of an object TOGETHER into one measure.

In the 1st law, momentum is ___________________.
And the net external force is ______________ . And linear momentum ___________ a ________ __________.
 conserved
 zero / none
 remains a constant value

2nd Law is the law of _____________________.
(what does it say?)
 Acceleration.
 FORCES CAUSE ACCELERATIONS;
 net external forces cause objects to speed up or slow down AND change direction
 the object will accelerate in the direction of the net external force
 the acceleration will be DIRECTLY proportional to the next external force and INVERSLY proportional to its mass.

2nd law: Linear impulsemomentum relationship!
∑F = ma
∑F t= m ∆v (change in momentum)
∑F t= m (v_{f}  v_{i}) (change in velocity)
Linear impulse measurement unit?
Linear momentum measurement unit?
 Newton second (Ns)
 kilogram meter per second (kgm/s)

3rd law=
equal and opposite froce (if not that case.... there is movement)
IN CONTACT; same magnitude applies but in OPPOSITE direction!

