Exam1 Flashcards
1
Q
Biomechanics Goals
A
-Improved performance & faster learning
-understand cause of injury
2
Q
Bio
A
Living or biological systems
3
Q
Mechanics
A
Study of forces & their effects on living systems
4
Q
Sport & exercise biomechanics
A
Study of forces & their effects on humans in exercise & sport
5
Q
Sport & exercise biomechanics goals
A
-performance improvement
-injury prevention
6
Q
Organization of mechanics
A
Rigid-body mechanics: Objects assumed to be perfectly rigid, simplifying analysis
Deformable-body mechanics: objects deform when loaded, related to training & injury
Fluid mechanics: mechanics in liquids + gasses (water & air)
Relativistic mechanics: Einstein’s theory of relativity
Quantum mechanics: quantum theory
7
Q
Statics
A
objects at rest/moving at constant velocity (Constant state of motion)
Acceleration = 0
No unbalanced force or torque acts on object
8
Q
Dynamics
A
Objects in acceleration motion; speeding up or slowing down (motion w/ acceleration)
Acceleration NOT = 0
Unbalanced forces & torques act on object
9
Q
Rigid-body mechanics are (2)…
A
Statics & dynamics
10
Q
What are the two Dynamics…
A
Kinematics & kinetics
11
Q
Levers: Force
A
Muscle
12
Q
Levers: Resistance
A
Weight or gravity
13
Q
Levers: Axis
A
Joint
14
Q
1st class lever
A
F.A.R
Ex: tricep dips, dumbbell overhead tricep ext, bench press, deadlift, Russian twist, pull up, front squat
15
Q
2nd class lever
A
A.R.F
Ex: standing calf raises (or seated), leg press
16
Q
3rd class lever
A
A.F.R
Ex: dumbbell bicep curl, hamstring curl, force pull, bicep curl, leg ext
17
Q
Torque
A
Eccentric force that causes rotation
18
Q
Force
A
-Push or pull by one object to another
-Pairs are = in size but act in opposite direction on each object
-Tends to cause each object to accelerate
19
Q
English unit
A
Pound
20
Q
SI unit
A
Newton (N)
21
Q
Magnitude
A
Size of push or pull
22
Q
Direction
A
Line of action (which way force is pushing or pulling)
23
Q
Point of application
A
Where the push or pull is applied on object
24
Q
Internal force
A
Pair forces act within object or system (inside the body)
Hold object together:
Tensile force- pulling (tension)
Compressive force- squeezing (compression)
25
External force
Acts on an object/system through interaction w/ environment (outside the body. gravity, friction, etc…)
Contact force : objects touch each other
Noncontact force: objects not touching each other
Gravitational force: weight of the object
26
What are Newton’s 3 laws…
1. Body at rest remain at rest, body in motion remain in motion until acted upon external force (inertia)
2. Force acting on object = to mass of object times it’s acceleration (F=ma)
3. Every action, there’s an = & opposite reaction (action-reaction)
27
F = ma
Force
28
Force can be?
Push or pull
29
Drawing a sketch of a dancer pushing off in a jump which of the following is NOT a force to consider?
The speed of the dancer across the floor
30
As normal contact force increases, what happens to the friction force ?
It increases
31
Force that acts PARALLEL to an object in contact with a surface is called ?
Friction force
32
Force that acts PERPENDICULAR to an object in contact with a surface is called ?
Normal contact force
33
Process of taking all the independent forces acting on an object & calculating the net force is termed ?
Force composition
34
If a scale shows an individual has a mass of 68kg, what’s that individual’s estimated weight?
680N
35
Which of the following situations do forces on a body sum to zero?
Horizontal forces (X) of -50N, -20N, +40N, +30N
(Put those numbers in calculator it’ll equal zero)
36
2 forces lying in the same plane are added together & the results is zero which is true ?
They are opposite in direction & equal in magnitude
37
Linear motion : all points on body move …
Same distance
Same direction
Same time
38
Rectilinear
Type of motion that moves in a Straight line
39
Curvilinear
Type of motion that moves in a Curved line
40
Angular motion: all points on body move…
Through same angle
Whole body rotation (giant swing)
Segment rotation (flexion, ext, etc…)
41
General motion (mixed)
Combines angular & linear motion
Ex: pedaling a bike, walking, drawing a straight line
42
Linear kinematics
Deals with motion of objects w/out forces (displacement, velocity, & acceleration)
43
Linear kinetics
Study of forces & their effects on motion of objects
44
Displacement
Straight line joining start and finish points in specified direction (vector)
X direction: horizontal
Y direction: vertical
45
Distance
measure Length of path traveled (Scalar)
46
Distance and displacement explanation
In a 400M race the length of path athlete follows (DISTANCE) is 400M but their DISPLACEMENT will be zero meters because they finish where they start
47
Resultant
Straight line between initial (start) & final (end)
48
Scalar
Has magnitude ONLY
Ex: speed, mass, volume, time
49
Vector
Has BOTH magnitude & direction
Ex: velocity, weight, friction
50
m/s
Speed
51
m/s squared
Acceleration
52
Speed
Distance traveled per sec (how fast you’re traveling)
Ex: car is traveling at speed of 60km/h
53
Velocity
Distance travelled per sec in specific direction (speed in given direction)
Ex: car is traveling at a speed of 60km/h in East direction
54
Acceleration
Any change in motion
Ex: starts, stops, speeds up, slows down, changes direction
55
V=d/t
Displacement divided by time
Velocity
56
Change in velocity divided by time
Acceleration
57
Force X Time
Impulse
58
Force is a
Vector quantity (has BOTH magnitude & direction)
59
Force is represented graphically with an
Arrow
60
Force is represented graphically with an arrow (explanation)…
Length of arrow = force magnitude
Arrow head= direction
Shaft of arrow= line of application
End of arrow= point of application
61
Weight
Force of gravity acting on an object
W=mg
W= weight in newtons
m= mass in kg
g= acceleration due to gravity =9.81 m/s squared downward
(9.81= 10m/s squared)
62
Contact forces
type of force that occurs between objects that are touching each other
Also called reaction forces
*each force acts separately on one of the objects*
63
Contact force can be resolved into what components?
Normal contact force: perpendicular to the 2 objects in contact
Parallel contact force: parallel to contacting surfaces of two objects (Friction force)
64
Friction
Opposes motion between 2 surfaces in contact resulting from interaction between surface molecules
65
Static friction
Two surfaces NOT moving on each other, while limiting friction is the maximum amount of friction that can be exerted before objects begin to slide
66
Dynamic friction
Two surfaces are moving on each other , also known as sliding friction or kinetic friction
67
Equation for friction
F= friction force (acts to oppose sliding)
u= coefficient of friction
R= normal contact force
Friction is proportional to the normal reaction force (R) pushing surfaces together and depends on the characteristics of the materials in contact, represented by the coefficient of friction (u)
68
Addition of forces: Force composition
Calculating the net or resultant force when multiple individual forces act on an object by vector addition
69
Net force
Sum of all external forces acting on one object also called resultant force, considering both their magnitudes & directions
70
What is the effect of two 100 N forces on an object?
depends on their directions:
If the forces are in the same direction: The net force will be the sum of the two forces, so the total force on the object would be 200 N in that direction.
If the forces are in opposite directions: The net force will be the difference between the two forces, so the total force would be 0 N (the forces cancel each other out).
If the forces are at an angle to each other: The net force would be found using vector addition, and the total force would be less than 200 N, depending on the angle between the forces.
71
Colinear Forces
One or more external forces w/ same line of action, with one assigned positive & the opposite direction negative
Ex: 2 people pulling on opposite ends of rope
72
Concurrent Forces
Forces are NOT colinear but act through same point
73
Static equilibrium
Object or system completely at rest with all forces acting perfectly balanced, resulting in no net force or motion
Body is not accelerating (no change in motion)
Forces are equilibrium (sum of 0 in all directions)
74
Rotation type of motion where whole body moves through same angle ?
Angular
75
When a runner has completed one full lap around a 400m track, what is the runner's distance with respect to the starting position?
zero
76
which type of motion describes the flight of a softball after it leaves the bat and sails in an arc over the outfield fence?
curvilinear motion
77
At 3 s into a run, a football player is traveling at +3 m/s. Four seconds later, the player is traveling at -5m/s. The change in velocity (v) is equal to
-8 m/s
78
which of the Newton's laws is described by the equation F=ma
Newton's second law
79
when a runner has completed one full lap around a 400m track, what is the runner's displacement with respect to the starting position
zero
80
velocity is calculated as
displacement over time
81
a softball is fouled with a vertical velocity of 20 m/s and a horizontal velocity of 15m/s. what is the resultant velocity of the ball
25 m/s
82
at 3 s into a run, a football is traveling at +3 m/s. four seconds later, the player is traveling at -5m/s. vf is equal to
-5m/s
83
newton's first law focuses on
inertia
84
at 3 s into a run, a football player is traveling at +3 m/s. four seconds later, the player is traveling at -5 m/s. the acceleration of the football player is
-2.0
85
unit of acceleration is…
m/s squared
86
velocity is related to displacement as speed is related to
distance
87
type of force between objects that are NOT touching
non contact
88
type of motion when body moves the same direction at the same time
linear
89
type of force that holds objects together by pulling
tensile
90
type of force that holds objects together by squeezing
compressive
91
linear kinematics
describes motion in terms of distance, direction, speed, and changes in velocity (acceleration)
92
position
Position refers to identifying an object's location in space using a reference point, which can be described in one, two, or three dimensions, such as along a line, within a coordinate system, or in relation to multiple axes.
93
Forces linked video notes
"force is a vector quantity (both magnitude & direction)"
"Normal contact force is that force b/w 2 objects that are acted upon by gravity that are holding them together"
"mechanical disadvantage in 3rd class levers, the moment arm of the muscle or applied force is smaller than the resistive force or weight they're trying to overcome"
94
gravity linked video notes
"convert N to lbs : 0.2248 X N"
"mass never change it stays the same but weight does change due to change of gravitational constants"
"gravitational constant is just acceleration due to gravity"
95
speed & velocity
both measure rate of motion
96
Instantaneous Speed or Velocity
rate of motion at an instant time
-Time duration very short
-Minimal change in position
97
Acceleration
Rate of change in velocity (Starts, stops, speeds up, slows down, changes direction)
Any change in motion
A vector quantity
98
Acceleration FACTS
Speeding up or starting: acceleration is in the same direction of motion
Slowing down or stopping: acceleration is in the opposite direction of motion
Sign of velocity & acceleration the SAME: body is speeding up
Sign of velocity & acceleration the OPPOSITE: body is slowing down
99
Uniform Acceleration
occurs when acceleration is constant, allowing prediction of future position and velocity
Two main applications:
-Vertical motion: gravitational force constant a = g = −9.81 m/s2 (−downward)
-Horizontal motion: ignore air resistance
acceleration = 0 m/s2
100
Kinematic Descriptors: Vertical Motion
vi = initial velocity
vf = final velocity
△y = y displacement
yi = initial position
yf = final position
g = gravitational acceleration = −9.81 m/s2
△t = time interval
ti = time initial
tf = time final
101
Kinematic Descriptors: Horizontal
Motion
vi = initial velocity
vf = final velocity
△x = x displacement
xi = initial position
xf = final position
= acceleration = 0 (air resistance negligible)
△t = time interval
ti = time initial
tf = time final
Horizontal velocity remains constant over time
102
Projectile Motion
An object in the air acted ONLY by forces of gravity and air resistance
Consider vertical and horizontal kinematics separately
Apply appropriate equation of uniform acceleration for each direction
103
impulse
Force X Time
104
Work equation
Force X Distance
105
power equation
Work divided by Time
106
what is the difference between velocity and speed?
Velocity is a vector quantity with both magnitude and direction, while speed is a scalar with only magnitude
107
how does force relate to mass and acceleration?
force is related to mass and acceleration by Newton's second law (F = ma)
108
example of a situation where work and power are important in biomechanics
in biomechanics, work and power are important in activities like sprinting, where work is done to move the body, and power is the rate at which the work is performed
109
Newton’s First Law: Mathematically
* v = constant if ΣF = 0
* v = instantaneous velocity
* ΣF = net force
110
Linear Momentum
* L = mv
* L = linear momentum (kg ∙ m/s)
* m = mass (kg)
* v = instantaneous velocity (m/s)
* Quantifies current state of motion and resistance to change
111
Newton’s First Law: Interpretation
* If an object is at rest, the net external force acting on it
must be zero
* If an object is in motion at constant velocity in a straight
line, the net external force acting on it must be zero
112
Conservation of Momentum
Rewording Newton’s first law:
* L = constant if ΣF = 0
* Useful for analyzing a group of objects (a system)
* All forces between objects are internal forces
113
Conservation of Momentum (continued)
If velocity of one object in the system increases, velocity of
another object decreases to conserve momentum
* Li and Lf are initial and final momentum, respectively
* m = mass of part of the system
* u = initial velocity
* v = final velocity
114
Elastic Collisions
* When two objects in a system collide head on and
separate, Σ(mu) = Σ(mv)
Coin experiment
* What happens?
* When one coin slows down, the other coin speeds up
* System momentum is conserved
115
Inelastic (Plastic) Collisions
When two objects in a system collide head on and stay together moving at the same velocity
116
Newton’s Second Law: Interpretation
* is a cause and effect relationship
* Forces cause acceleration
* Acceleration is the effect of forces
If a net external force acts on an object, the object
accelerates
* If an object accelerates, a net external force must be acting
to cause the acceleration
117
Impulse and Momentum
Acceleration at an instant in time
* Usually more concerned with final velocity after external
forces act on the object for a period of time
* Substitute into
118
impulse
Impulse: Force applied to an object for a certain amount of time
* Impulse causes change in momentum
* Mass usually constant, impulse changes velocity
119
impulse to increase momentum examples
* Throwing
* Hitting
* Push-off
* Thrust
(increasing duration of force
in a specific direction)
120
Impulse to decrease momentum
* Catching
* Landing
* Giving
* Safe performance involves increasing duration of force
application to reduce the force magnitude
* Landing mats
* Helmets
* Footwear
121
Law of Universal Gravitation
* All bodies are attracted to one another with a force
proportional to the product of their masses and inversely
proportional to the square of the distance between them
* For our consideration, performance on earth (a large mass)
122
crash course video notes
"time, position, velocity, and acceleration all relate to each other"
"average velocity is the change in position over time and average acceleration is the change in velocity over time"
"figuring out how much something is changing just mean that you have to subtract its starting value from its final value"
