# Biomechanics 1

As the surface area of two objects in contact increases, what happens to the force of friction?
remains constant
The force that acts parallel to an object in contact with a surface is called-
friction force
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The force that acts perpendicular to an object in contact with a surface is called-
normal contact force
As the normal contact force increases, what happens to the friction force?
increases
push or a pull
forces
When drawn, the length of a vector describes it-
magnitude
A free-body diagram displays:
forces acting on a body
Concurrent forces are forces that-
act through same point
To fully define a vector quantity, you must specify-
direction
magnitude
the process of determining each of the forces that combine to make up a resultant force is called-
force resolution
units of accelerations are-
m/s^2
what factor differentiates velocity from speed?
direction
velocity is calculated as-
displacement/time
what term best describes linear motion along a curved line?
curvilinear
acceleration describes the time rate of change of-
velocity
elbow extension takes place in what plane?
sagittal
abduction occurs in which plane?
frontal
the cardinal frontal plane divides the body into equal _____
front and back halves
movements in transverse plane occur around which axis?
longitudinal
Examples of sagittal plane movement-
flexion
extension
plantar flexion
description used when one of intersecting lines in immovable relative to the earth
absolute angular position
description used when both intersecting lines are capable of moving
relative angular position
considered the starting point for all body segment movements (starting point of motion)
anatomical position
divides body vertical into left and right halves
ex- running, summersalt
sagittal plane
divides body into front and back halves
ex- jumping jacks
frontal plane
divides body into top and bottom halves
ex- spins, pirouette
transverse plane
imaginary line passing through body from side to side
transverse axis
sagittal plane rotation occurs
transverse axis
passing from front to back through body
anteriorposterior axis
frontal plane rotation occurs
anteriorposterior axis
passes from top to bottom
longitudinal axis
transverse plane rotation occurs
longitudinal axis
each axis is associated with the plane it is __________ with
perpendicular
orientation of a line with another line
angular position
change in absolute angular position experienced by a rotating line
angular displacement
force that is exerted by one object on another ________
action
force is matched by an equal but opposite force exerted by the second object _______
reaction
units of force
Newton N
internal forces
tensile
compression
-internal force that pulls
-ligaments are stretched
-rubber band
tensile
-internal force
-pushing force action on the end
-sponge. (ex- spinal compression)
compression
contact forces always come in pairs _____ & ________
action
reaction
gravitational acceleration
9.81 m/s^2
weight (N)
mass * gravity
example of contact force
shot putter
jumping
parallel to surface in contact
friction
interaction between molecules of the surface in contact
dry friction
friction that acts between two surfaces that are not moving relative to one another
static friction
what is proportional to normal contact force
frictional force
what acts perpendicular to the normal contact force and parallel to the surface
frictional force
________ is affected by material type in contact with the surface
frictional force
mathematical description of static friction force-
(F)= mu*R
In friction equation (F)= mu*R
what does R stand for?
normal contact force
mathematical representation of any quantity defined by size/magnitude and direction/orientation
vector
length of vector =
magnitude
vectors line of application =
orientation
direction of vector =
determining a single vector from two or more vectors by vector addition
vector composition
replaces a single vector with two perpendicular vectors
vector resolution
if vectors are same direction you _______ magnitudes
if vectors are in opposite direction you_________ magnitudes
subtract
-this is the sketch of system and all external forces acting on it
-representation of all external forces and moments acting on the system of interest
free body diagram
an object is in ________ equilibrium if all forces are balanced
static
-person isn’t accelerating
-person ins’t moving, the sum of all forces acting on them must be 0
static equilibrium
where something is located in space
-1 dimensional, 2 dimensional
position
length of the path followed by the object from initial to final position
-direction is not important
distance travelled
-direction of movement is taken into account
-straight line distance from initial to final position
-vector quantity
average displacement
distance travelled divided by the time it took to travel that distance
average speed
=distance travelled/total duration

average speed (m/s)
displacement of an object divided by time it took for that displacement
average velocity
=displacement/total duration
average velocity (m/s)
________ is the rate of motion
speed
is the rate of motion in specific direction (rate of displacement)
-vector quantity
velocity
these are the same if motion is in a straight line with no change in direction
ex- sprint, walking, swimming
speed
velocity
measured over an instant of time rather than a total duration of time
instantaneous speed and velocity
rate of change of velocity
average acceleration
=change in velocity/total duration
average acceleration (m/s^2)
object ___________ if magnitude of velocity is changing
accelerates
ex= “5 meters per second east”
(if change in speed, direction, or both)
velocity
ex= how *fast a car is being driven, how *quick a jaguar runs
speed
you are ________ when you change speed or direction
ex= car speeding up after stopping at a red light
accelerating
in anatomical position, the forearm is in what position?
supinated
Which of the following limb movements dominate during jumping jacks?