3.2.2.6 Fluid mechanics

Question 1

fluid friction (drag) 
laminar

Answer 1

flowing of air or water past an object
depends on:
1. laminar flow (flow in layers) -> assisted by streamlining
2. smooth

Question 2

fluid friction (drag) 
vortices

Answer 2

vortices formed fluid doesnt flow smoothly
bits of fluid flung randomly sideways
cause drag
bits of fluid dragged along with moving object (cycling helmet)

Question 3

air resistance is dependent on..

3 things

Answer 3

1. size
2. shape
3. speed of object

Question 4

fluid mechanics

Answer 4

study of an object/human body travelling through any liquid or gas
fluid environment can affect variety of sports
1. drag 2. upward lift force 3. downward life force

Question 5

fluid friction (drag)

Answer 5

force act opposite direction to motion = slow down

greater velocity of body travel in fluid = greater drag

depends on laminar flow (streamlining assists)

Question 6

fluid friction depends on:

4 things

Answer 6

of moving object:

1. shape (streamlined/aerodynamic = reduce drag)
2. cross sectional area (larger= increase drag)
3. velocity
4. surface characteristics

Question 7

examples of factors affecting fluid friction

Answer 7

e. g. cyclist change body position (swimmer also) leans forward /crouches/tucks arms in = decrease cross sectional area = less of their body exposed to air
e. g. cyclist wear lycra, swimmer wear hats (surface characteristics) = reduce surface drag - cycle at high speed
e. g. shape of helmets for cyclists, shape of sports vehicles car/bike curved cars - less turbulence - lamina flow
e. g. cyclist wear streamlined helmet = reduce turbulence - lamina flow

Question 8

lamina flow

Answer 8

air flows smoothly around the object
smooth flowing of air or water past an object
flowing in layers

Question 9

2 types of drag:

Answer 9

1. surface drag

2. form drag (shape drag)

Question 10

surface drag

Answer 10

friction between surface of an object and the fluid environment
-swimmers =specialised clothing & shave = reduce SD

Question 11

form drag (shape drag)

Answer 11

impact of fluid env on an object
forces affecting leading edge of an object increase form drag and forces affecting trailing edge reduces form drag (streamlining)

swimmer = reduce form drag = thinest/straightest form as move through water

cyclist = reduce form drag through drafting= large form drag offers less turbulent air for anything following e.g. slipstream

Question 12

high values of fluid friction

Answer 12

sports person/vehicle moving through water = high

= fluid friction is critical factor governing speed

Question 13

drafting in cycling

Answer 13

wind hits 1st cyclist = gos round the sides = pockets of air behind them = the effect is greater the closer you are

Question 14

shuttle cock example

Answer 14

turbulent flow = increase air resistance

low mass and large drag force (due to shape/holes/feathers)

Question 15

drag is low when

3 things

Answer 15

1. object moving slow
2. smooth surface
3. high mass

Question 16

impact of fluid friction examples

Answer 16

e. g. sprinter/games players, fluid friction = much less than friction effect/weight (streamlining less important)
e. g. shot/hammer in flight = fluid friction much less than weight, angle of release 45 degrees

Question 17

turbulent flow/vortex flow

Answer 17

vortices formed fluid doesnt flow smoothly
bits of fluid flung randomly sideways = drag
bits of fluid dragged along with moving object (cycle helmet)

Question 18

Bernoulli principle

Answer 18

air molecules exert less pressure the faster they travel
air molecules exert more pressure the slower they travel

create a lift force = force causing body to move in perpendicular direction to direction of travel= more lift of projectile = longer stay in air - further horizontal distance travel
AEROFOIIL

Question 19

angle of attack (AofA)

Answer 19

angle travelling through air
tilt of projectile relative to air flow

AofA increase too much = drag increase - projectile stall 
optimum angle (25-40)

Question 20

pressure vs speed

Answer 20

moving slower = less distance to travel = more pressure

moving faster = further to travel = less pressure

Question 21

downward lift (racing car)

Answer 21

move faster underneath = less pressure, want to move slower on top = more pressure = downward force

Question 22

drag force

Answer 22

force that acts in opposition to motion

negative effect on velocity

Question 23

streamlining

Answer 23

shaping a body so it can move effectively and quickly through a fluid

Question 24

3 factors that increase/reduce drag

Answer 24

1. velocity of moving body: faster = greater drag = greater AR (streamline)
2. cross sectional area: large = increase, crouching down in cycling = travel faster
3. shape/surface characteristics: streamlined/aerodynamic reduces drag e.g. speed skier (helmet), cycling helmets

badminton shuttlecock = larger drag from AR = lose speed quickly

Question 25

lift force

Answer 25

causes body to move perpendicular to direction of travel

Question 26

aerofoil

Answer 26

shape/object where air over the top travels further than the bottom

Question 27

object has to travel further

Answer 27

travels at a faster speed

exerts less pressure

Question 28

object has to travel less distance

Answer 28

travels at a slower speed

exerts more pressure