linear motion Flashcards
letters for SUVAT
S = displacement
U = intial velocity
V = final velocity
A = acceleration
T = change in time
pros of embedded force plate
-accurate and reliable 3D force measurements
-high sampling frequency + resolution
cons of embedded force plate
-ecological validity (cannot recreate outside activity)
-expensive
portable force platform pro and con
:) cheaper
:( slightly worse reliability, validity, resolution
pros of triaxial accelerometer
measure instantaneous acceleration
comment on triaxial accelerometer
need to know what you’re using it for in order to assess whether it is reliable and valid
pros of accelerometer position
-cheaper than lab based equipment
-easy to use
cons of acclerometer position
-battery life
-does it affect the movement being monitored?
impulse is the
change in momentum
impulse (Ns) equation
force (N) x time (secs)
moments can sometimes be called
torques
moment equation =
force x perpendicular distance
friction is …
a force that acts in opposition to the movement of one surface over another
friction equation =
coefficient of friction x normal force
name the three types of friction
static, sliding, rolling
the coefficient of friction is between 0 and 1, what does closer to 1 mean?
closer to 1 = more friction
closer to 0 = less friction
why is static friction higher than dynamic friction?
because it is harder to start something moving than it is to keep something moving
what is air/water resistance?
the friction of something moving through something
equation for drag force FDRAG
0.5 p v2 Cd A
what do the letters stand for in the drag force equation
p = density of the fluid
v = relative velocity squared
Cd = drag coefficient
A = surface area
what will happen if relative velocity is doubled?
drag force is x4 quadrupled (because velocity is squared)
how to calculate velocity in opposite directions
the sum (add +)
how to calculate velocity in the same direction
the difference (minus -)
the higher the drag coefficient …
the more drag force there is
LAMINAR air flow
-fluid slides smoothly
-layers flow in parallel
-little disruption to fluid
TURBULENT air flow
-slows objects
-boundary layer composed of vorticles that increase friction
-more disruption
turbulant flow causes
whereas laminar flow
more friction
causes less resistance to movement
methods of reducing drag
-more streamlined shape -> to change your drag coefficient
-smaller surface area -> to reduce the amount of drag
-slower relative velocity -> in drafting (e.g., cycling)
greater relative velocity means that there is
-> more disturbance of the fluid around the object
-> have to work harder to overcome fluid forces
