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Biomechanics
Biomechanics Exam 2
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Gravity
Terms in this set (74)
motion
change of position in space relative to a frame of reference
distance (L-lowercased)
the simplest linear motion variable
angular motion example
car revolutions of tires
linear variable example
measurement of distance the car travels
displacement
corresponding vector quantity to distance
reference frames
global (fixed or inertial-earth); local (other moving object). both can be measured in 1D, 2D, and 3D. 2D (on plane with two linear coordinates x,y). 3D with three (x,y,z)
linear displacement
usually defined relative to right angle directions
2D degrees of freedom: point mass
whole body mass acting at one point in space
degrees of freedom
constraints in coordination, limits degrees of freedom used in early motor learning (kid kicking a soccer ball or shooting a basketball for the first time)
displacement (d)
change in position= final position-initial position (+ or - signs refers to change in position)
vector quantity
has both magnitude and direction
vertical height
standing height/stature
velocity (v)
vector quantity that describes the rate of change of displacement
speed (s)
scalar quantity that describes rate of linear position without regard to direction (s= change of l/change in t)
acceleration
vector quantity that describes the rate of change in velocity (acceleration can speed up, slow down, and/or tend to change in direction)
relative frame of reference
measuring a point that is also free to move, like the motion of the foot relative to the hip or the plant foot relative to the soccer ball
three phases of acceleration
positive acceleration (when a swimmer pushes off the wall and is gaining speed), near zero acceleration (when a swimmer is at top speed), negative acceleration (when a swimmer is about to slow down at the wall)
distance, not height
if the angle of projection is below 45 degrees what are you going for?
height, not distance
if the angle of projection is above 45 degrees what are you going for?
goal (speed, displacement, accuracy), initial angle of projection, projection speed, height of release, object spin, projectile properties (mass, shape, size), wind.
optimal release conditions projectiles factors that could influence trajectory and displacement
angular displacement
change in angular position in a specified direction. absolute angle (fixed frame of reference) vs. relative angle (moving frame of reference)
angular velocity
rate of change in angular position in a specified direction
angular acceleration
rate of change in angular velocity in a specific direction (think of as an unbalanced moment in a particular direction)
Goniometer (one way to measure static flexibility)
angular displacement is measured with what?
coordination continuum principle
movements requiring high forces tend to use simultaneous joint coordination, and movements requiring lower force and higher speed tend to use sequential joint coordination
FM pattern
movement category (run, jump, throw, strike, kick, catch, carry...)
skill
FM pattern adapted for a specific activity (punt, high jump, softball pitch...)
technique
a type of skill (fastball, curveball, hang, hitch-kick...)
style
personal, idiosyncratic specialization of movement technique
statics
forces on bodies equal to 0 (motionless or uniform motion)
dynamics
forces on bodies not equal to 0 (accelerated motion)
force
push or pull; forces are straight line effects between two bodies that tend to accelerate or deform
force platform
measures reaction forces and moments applied to the surface in all three dimensions. (usually ground reaction forces (GRF))(when you plant your foot before kicking a soccer ball). (examples of weights on the ground)
inertia
anybody continues in a state of rest or uniform motion unless an unbalanced force acts on it
momentum
the acceleration a body experiences is proportional to the force causing it in the same direction
reaction
for every action (force) there is an equal and opposite reaction (force)
inertia in newton's 1st law of motion
the property of all matter to resist change in its state of motion. mass is scalar
inertia
reduce it to facilitate acceleration (agility); increase inertia to facilitate stability and resistance to external forces
newton's 2nd law of motion
the acceleration of an object increases with increased force, and decreases with increased mass. the acceleration is in the same direction as the net force.
newton's 3rd law of motion
for every action (force) there is an equal and opposite reaction (force) (example where he talked about throwing shit to get out of a platform that is slippery or no friction)
impulse (j)
the mechanical effect of a force acting over time
momentum (p)
quantity of motion of an object. defined as product of mass and velocity. is a vector (two football players hitting each other)
impulse-momentum relationship
they are very similar; same impule=same momentum. (think about when you jump as high as you can the more impulse you take the higher you jump)
mechanical energy
the capacity to do work is scalar
work
the product of force and the displacement in that direction (scalar) (w=Fxd). work has no relationship to time or effort
ergometer
what do you measure work or energy with?
power
the rate of doing work (scalar) P=w/t or p= F x V
B
Q5#1: the vector linear kinematic variable documenting motion is
A. speed
B. displacement
C. Distance
D. Velocity
D
Q5#2: the optimal projection principle determines the most successful angles to
A. increase time of object flight
B. increase the distance of object flight
C. match an ideal trajectory
D. achieve a particular goal
B
Q5#3: whcih of the following is a scalar quantity?
A. horizontal velocity
B. speed
C. vertical velocity
D. gravitational acceleration
D
Q5#4: acceleration should be thought of as
A. speeding up
B. slowing down
C.a change in direction
D. action of an unbalanced force in a particular direction
D?
Q5#5: the coordination principle of biomechanics indicates sequential coordination would be expected most often in
A. a dead lift
B. a vertical jump
C. a lunge
D. a baseball pitch
B
A dancer needs to make it from one side of the stage to the other in only 3 jumps. what should she do to increase the horizontal displacement of each jump?
A. take her time on each jump for a take-off angle of > 45 degrees
B. try to jump quickly so each jump is < 45 degrees
C. try to jump exactly at 45 degrees
D. not enough information to answer
C
a quantity that can be defined by magnitude only is:
A. weight
B. velocity
C. scalar
D. vector
E
A child clowning around in the gym kicks a ball from rest on the free throw line is surprised to find that the ball passes cleanly through the hoop. which of the following is likely true about this event?
A. the ball had 10 feet of net vertical displacement to the goal
B. the ball followed a parabolic path
C. there was little air resistance
D. the time up did not equal the time down to the goal
E. all true
C
a person wanting to run to the right must push with their legs:
A. to the right
B. forward
C. to the left
D. backward
D
a hockey player (A) skating to the right at 15 m/s is checked in the opposite direction by an opponent (B). which of the following is true about this event?
A. a positively accelerates
B. a increases his velocity
C. b negatively accelerates
D. b positively accelerates
B
an example of a relative angle is the:
A. trunk lean in running
B. knee angle in walking
C. angle of release in throwing
D. angle of the foot relative to the ground
A
Which of the following kinetic variables does not depend on time?
A. work
B. power
C. momentum
D. impulse
B
In catching or throwing a water balloon, what mechanical variable should be minimized?
A. impulse
B. peak force
C. momentum
D. time
C
a gymnast is performing a backwards 1 1/2 somersault in a tuck position. while she is in the air, what is her vertical acceleration of her center of gravity?
A. first negative, then positive
B. always upward
C. always downward
D. varies with body position
A
which of the following is a kinetic variable?
A. weight
B. speed of an athlete
C. hamstring range of motion
D. angular velocity of hip extension
D
what does a vector tell us that a scalar doesn't?
A. units of measure
B. mass
C. size
D. direction
B
the time of integral of force is:
A. moment
B. Impulse
C. energy
D. work
D
the greek letter delta is used to represent:
A. time
B. speed
C. displacement
D. change in
D
the force of dry friction depends on:
A. elasticity
B. coefficient of friction
C. normal force
D. both b and c
B
the horizontal acceleration of a sprinter is usually zero:
A. during the first few strides
B. at peak speed
C. the last few strides
Angular displacement is the change in angle, angular acceleration is rate of change of angular velocity
what is the difference between angular displacement and angular acceleration?
simultaneous
___ coordination is normally used when moving large mass objects
45
at what angle should a soccer ball be kicked to go the farthest if it lands at the same level as it was kicked and there is no air resistance?
less than 45
at what angle should a soccer ball be kicked to go the farthest if it lands at the same level as it was kicked and there is air resistance?
the property of all matter to resist change in its state of motion (newtons 1st law)
what is the inertia principle of biomechanics?
distance divided by time
if a ball is thrown by a pitcher that travels 20m to the catcher in .5 seconds, what is the average speed of the ball?
one rotation per minute
the second hand of an analog clock has what angular velocity?
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