Exam 1 Flashcards
Biomechanics definition
The study of movement of living things using the science of mechanics
Rigid Body
a shape that cannot be moved or changed
a solid body in which deformation is zero or so small that can be neglected
Rigid Body Mechanics
assuming the bodies are rigid, these bodies will not deform under the action of applied forces
Kinematics
the motion
Kinetics
the cause of the motion
Why do we study biomechanics
- to improve athletic performance
- reduce injury risk by identifying the mechanics that resulted in the injury as well as the mechanics that came from the result of the injury
Ways to achieve the two goals of biomechanics
- modify movement technique
2. Equipment research and development, eg= prosthetics
qualitative
non-numeric, unstructured
quantitative
numeric, structured
Sagittal Plane
separates the left and right sides of the body
Flexion and extension occur here
Transverse Plane
Separates superior and inferior (upper half and lower half)
Internal and External rotation occur here
Frontal Plane or Coronal Plane
separates anterior and posterior; ventral and dorsal
Axis of Motion
the hinge or the pivot point around which movements occur
3 that we study are mediolateral, anteroposterior, longitudinal
Mediolateral Axis
lateral, perpendicular to the sagittal plane
Anteroposterior Axis
Perpendicular to the frontal plane
Longitudinal Axis
Perpendicular to the transverse plane
Flexion
Bending, contracting
Sagittal plane
Extension
straightening, lengthening
Sagittal plane
Internal Rotation
limb rotates toward the midline
transverse plane
External Rotation
limb rotates toward the lateral part of the body
transverse plane
Abduction
movement away from midline
frontal plane
Adduction
movement towards the midline
frontal plane
Radial/Ulnar deviation
occurs in the frontal plane, hand movements
Dorsiflexion
toes go to the sky
Plantar flexion
toes curl
Inversion
going towards midline (internal rotation)
transverse plane
Eversion
goes away from midline (external rotation)
transverse plane
Shoulder Joint Flexion
arms go above head
Shoulder Joint Extension
arms go behind body
Supination
palm up
Pronation
palm down
flexed vertebral column
bend towards knees, head down
extended vertebral column
leaning back
Observation in biomechanics
best viewing angle # of viewing angles distance # of reps equipment clothing and background location
Evaluation
identify errors
evaluate errors
-cause, impact, safety
Instruction
clear communication, learning time
Body of kinematics
the object of analysis
System of Kinematics
the object of analysis that is made up of two or more bodies
Frame of Reference
perspective from which movement is described
-origin, direction
Postition
an objects location in the frame of reference
scalar
magnitude only-speed, time, volume, mass etc
vector
magnitude and spatial direction-velocity, force, displacement etc
Velocity
change of position/ change in time
total displacement/total time
acceleration
change in velocity/change in time
v1-v/t1-t
taken in increments/segments
negative acceleration
slowing down in a positive direction
speeding up in a negative direction
Slope of a position vs. time graph
average velocity: the velocity taken over the defined interval
Instantaneous Velocity
velocity @ specific time and space point
Slope of a Velocity vs Time graph
average acceleration
Shaded area under the velocity line (velocity vs time graph)
displacement
Vf=Vi + at
use if acceleration, time or a initial velocity is given or you need
d= Vit + 1/2a^2
distance, velocities, accelerations and time
d= 1/2(Vi + Vf)t
distance, velocities, time
Vf^2= Vi^2 + 2ad
distance, acceleration, velocities
Plane
smooth, flat space defined by two axes
Planar Motion
any motion in said plane
Projectile
any airborne body that is only subjected to gravity and wind/air resistance after it has left the ground
Trajectory
the path of the projectile
Apex
vertical velocity= 0 m/s
the highest point of trajectory
Parabola
created by vertical and horizontal projectile
* if air resistance is not significant and no other forces acting on it then Vh is constant at each time point
Horizontal motion
Affected by air resistance
Vertical Motion
affected by gravity
Gravity
9.81 m/s^2
if the object is traveling towards the earth then the magnitude of gravity is positive 9.81
Final Vertical Displacement equation
Yf= Viy+delta time+1/2g(deltatime^2)
Final Vertical Velocity
Vf=Viy + g(deltatime)
Angular Kinematics
an object rotating around an axis
clockwise motion
negative
counterclockwise
positive
angular position (theta)
how far a body is rotated form its reference
degrees or radians
Radian
s/r
s= arc length
r= radius
1 radian = 180/pie, measure of the central angle whose arc length equals the radius of the circle
degrees to radians
multiply by pie/180
radians to degrees
multiply by 180/pie
Angular Displacement (delta theta)
change in angular position b/w two time periods of interest
Angular Velocity (W)
how fast a body is rotating in a particular direction
w= angular displacement/change in time
units: degrees/sec or radians/sec
convert to radians first
Angular Acceleration (a)
time rate of change in angular velocity
how quickly an object is speeding up or slowing down it’s rotation in a particular direction
a= Change in angular velocity/ change in time a= deltaW/deltat
Arc Length (s)
distance b/w two points along a curve section, degrees
Tangential Velocity (v)
direction of the velocity vector (v) is perpendicular to the radial axis and in the direction of the motion
v= r*w
Force
a push or pull results from physical contact b/w two objects
a vector quantity
Newtons
N
kg/m/s^2
1lb= ? N
4.448N
1 N = ? lbs
.225 lbs
colinear force
forces that have the same line of action
these forces can be added together
these forces can be in opposite directions
Vector Addition
tail-tip
Internal Forces
tension force
compression force
Tension Force
pulling forces act on the ends of an internal structure
structure is under tension
Compression Force
pushing forces act on the ends on an internal structure
structure is under compression
What happens when tension and compression forces are greater than the body?
the structure can not withstand the forces and therefore the structure fails, resulting in injury
External Forces
Contact
Non-contact
Contact Forces
ground reaction forces, forces that act on each other
Non-Contact Forces
ex. gravity, air resistance, friction
Friction
acts in opposition to the intended motion of the object
Static Motion
the Fmax=F therefore the net force= 0
Fmax
max static friction force
First Class Lever
Axis of rotation is in between the effort and the load
Second Class Lever
Resistance/Load force is in between the effort force and the axis
Third Class Lever
Effort Force is in between the axis and the Load/Resistance force
Static Equilibrium
Net force and Net Torque both equal 0
Rigid Body Length
equals the radius
rotational curve length
radians x radius
**convert degrees to radians (3.14/180) before multiplying by the radius
Tangential Velocity
w x r
r= radius= rigid body length
Vector Quantities
magnitude and direction
Force, torque, velocity
Scalar Quantities
magnitude only
speed, volume, mass, time
Slope of a position vs. time graph
average velocity
Slope of velocity vs time grapsh
average acceleration
instantaneous velocity
velocity between two designated time periods
