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Bio-mechanics Exam 5
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Gravity
Terms in this set (61)
Orientation of a line with another line or plane
example:
the tibia and femur flexed at a right angle. the femur is one line and tibia is other
Angular Position
an angle (describing "theta") is an Intersection of:
(could be 3 things)
Two lines
Two planes
One line and one plane
_____ is the angle present at Intersection of Two lines, Two planes, or One line and one plane
theta
Difference between absolute and relative angles
view slide 6
(in angular position)
What is absolute position?
the reference line is fixed (ground)
(in angular positon)
what is relative position?
the reference line is movable (limb)
angular units depend on what?
situation
what are the three ANGULAR units (depending on situation)
1- RPM's
2- Radians
3 -Degrees
_______ is a angular unit of measurement that is noted by Large angular distances over long time (mins. or secs)
RPM's
what angular unit's Degrees are too messy.
example: Rotational speed of car engines, music CDs/DVDs, dental drills, etc.
RPM's
RPM's stands for
revolutions per minute
_______'s are an angular unit of measurment that specifies that there are 360 of them in a complete circle
degrees
How do you compare linear meters to angular degrees?
Convert degrees to radians
_______ are an angular measure that use the radius' length (linear) to measure the arc length (angular)
Radians
RPM's, Radians and degrees are all ?
measurments (units) of angular positon
Linear length of arc path when straightened out
L = (this)
Arc Length
Radian = (formula)
Radian (theta) = arc length (l) / radius (r)
_______ tell how many radii (radius) are in a given arc length. and its numerical value is a ratio of
**arc length / radius
Radian
true/false?
Radians are a "unit-less" ratio
true
When the arc length equal the radius length then you have ______ Radian(s) or 57.3º
1 (one)
one radian is = to _____ degrees
57.3
one radian = 57.3 degrees, so in a circle there are ____ radians
6.28 radians
how many radians are in a half circle? how many degrees is that?
3.14 radians
or 179.9 degrees
how many radians are in a quarter of a circle?
how many degrees would that make?
1.57 radians,
or 89.96 degrees
(In angular distance vs. angular displacement)
what displacement means is?
the difference of final and initial position
displacment = final - initail
(In angular distance vs. angular displacement)
what distance means is?
the DEGREES traveled along the arc path
Angular Displacement = ∆(theta).....what is the formula that = ∆(theta)
(theta) final - (theta) initial = ∆(theta)
angular distance (finding the distance a runner ran around a circular track) how does the formula look?
L = arc length = the distance ran from start to finish
so L = ∆(theta) x (radius)
(displacment DIRECTION)
counter-clockwise = a _____ direction
positive
clockwise =
negative
Strength Disadvantage: Small lever-arm, requires _________ muscle force
a) more
b) equal
c) less
a) more
Speed/ROM Advantage: _______ end of limbs move a greater angular distance (arc length)
a) proximal
b) distal
c) anterior
d) long
b) DISTAL
________'s "amplify" motion of limbs
implements
Bats, clubs, sticks, etc. apply greater ____________'s to objects
...
strength-velocity tradeoff in sports:
which one is at an disadvantage?
strength
strength-velocity tradeoff in sports:
which one is at an advantage?
veloctiy (speed/ROM)
sigma = (∆l) / (∆t)
what is this for?
average angular speed
average angular speed = the rate of ________ traveled
(l) arc-length
omega = ∆(theta) / ∆t
what does this figure out?
average angular velocity
Rate of change in angular displacement
average angular velocity
Rate of arc-length traveled
average angular speed
When there is a long time taken to rotate through a given displacement (gymnasts, divers, skaters.)
_______ more useful; speed & velocity can differ
Average or Instantaneous?
average
When a short time (linear velocity) taken at release (throw), impact (strike) or takeoff (jump).
_______ more useful; speed & velocity are basically the same
average or instantaneous?
instantaneous
true/false?
linear velocity (v) relates to angular velocity.
true
which is more useful? (instantaneous or average)?
rotation in a figure skater.
average
which is more useful? (instantaneous or average)?
velocity of a baseball from a pitchers hand?
instantaneous
if three different lines have the same radian but different radiu(s) then they are traveling at the same time interval, but covering different arc lengths.
this is expressed in ___________ vs. instant angular v
instant linear
linear velocity = (theta in Rad) x (____)
radius (r)
____________ = Instant Angular (sigma) x radius
Instant Linear (v) velocity
v = (sigma) x r
is the expression for
Instant Linear v
v = (sigma) x r:
so...V direction is ________(perpendicular to radius)
tangent
Two balls hit at same time. One is 20 cm from the bat's axis, the other is 40 cm away. If the bat's (sigma) is 30 rad/s at the instant of contact, what are the linear velocities (v) of the bat at the points where both balls are hit?
...
(sigma) =
angular velocity, which is ∆(theta or rad) / t
Rate of change in angular velocity.
Units: º/s2 (or rad/s2)
angular acceleration (alpha)
alpha = ∆(sigma) / ∆time
same as... = (sigma)final - (sigma)inital / ∆t
this is the formula for?
angular acceleration
true/false:
Angular (alpha) is Two Linear Accelerations (a)
true
When angular velocity increases so does the linear velocity.
This relationship exists with angular and linear _________s as well.
...
__________ Acceleration: "A-t" affects magnitude only
Tangential
______ Acceleration (Centripetal): "A-r" affects direction only
Radial
Linear acceleration tangent to the circular path of a rotating object
Tangential Acceleration (A-t)
formula expressing _________ acceleration
A-t = (alpha) x r
...
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