9.3- Fluid mechanics and projectile motion Flashcards
What is fluid mechanics
study of the forces acting on a body travelling through the air/ water
Name the issues air resistance and drag pose against an athletes body
air resistance and drag act against the motion of a body
-place an increased psychological demand
-can lead to early fatigue and poor performance
Name the 4 main factors that affect the
magnitude of air resistance and drag on a body
-velocity -> greater the velocity -> greater the force of air resistance/drag opposing their motion
-frontal cross -> low crouched psotion of a downhill skier reduces air resistance & drag
-streamlining and shape -> more aerodynamic the shape of a body/ equipment -> lower the air resistance/ drag
-surface characteristics -> e.g. increased smoothness -> lycra swimsuits reduce air resistance
How does velocity affect magnitude of air resistance and drag
-greater the velocity the greater the air resistance or drag
Name 3 sports that are affected by air resistance and drag due to their high velocities
-track cycling
-speed skating
-freestyle swimming
How does frontal cross affect magnitude of air resistance and drag
larger the frontal cross, the larger the air resistance or drag
Name 2 sports that are affected by air resistance and drag due to their large frontal cross
-track cycling
-downhill skiing
How does streamlining and shape affect magnitude of air resistance and drag
more streamlined/ aerodynamic the shape of the body in motion- lower the air resistance or drag
What is aerofoil
streamlined shape with curved upper surface and flat lower surface designed to give an additional lift force to a body
What is streamlining
creating of smooth air flow around aerodynamic shape
-the more aerodynamic the shape of a body the lower the air resistance
How does surface charcteristics affect magnitude of air resistance and drag
smoother the surface the lower the air resistance and drag
Give examples of how downjill skiers battle air resistance to maximise performance
-minimise frontal cross –> low crouch position
-wear tear-drop-shape helmets –> streamlined shape
-wear super silky lycra suits –> smooth surface
Give examples of how track cyclists battle air resistance to maximise performance
-lightweight bike with aerdoynamic features –> disc wheels
-aerodynamic riding position -> shoulders forward
-aerodynamic helmets
-tight fitting lycra skin suits- smooth socks pulled over shoes
What is projectile motion
movement of a body through the air following curved flight path under force of gravity
What is a projectile
body launched into air and subjected to weight and air resistance forces
Give 2 examples of the 2 types of projectiles
-athlete (high jumper)
-equipment thrown, hit, kicked (javelin, tennis ball)
What occurs when a projectile is in flight
projectiles follow a flight path through the air
-flight path from start - finish shows overall distance travelled
What graph can be used to show the flight path a projectile takes
graph of height against horizontal distance travelled
Name the 4 factors that affect the distance travelled by a projectile
-speed of release -> greater speed of projectile, further it will travel
-angle of release -> 45 degrees -> optimal angle to maximise horizontal distance
-height of release -> 45 degrees -> optimal angle if release height and landing height are equal
-where release height is ^ than landing height, optimal angle is less than 45 degrees
-aerodynamic factors (Bernoullli and Magnus) ->
How is the horizontal distance travelled by a projectile affected by the speed of release
(newtons 2nd law)- greater the force applied to projectile - greater the change in momentum - further projectile accelerates into air
-greater the outgoing speed of the projectile, further it will travel
How is the horizontal distance travlled by a projectile affected by the angle of release
-90 degrees- projectile will accelerate vertically upwards and come straight back down- travelling 0m
-45 degrees- optimal angle to maximise horizontal distance
-60/ 75 degrees- projectile reaches peak height too quickly- rapidly returns to ground
-30 degrees- projectile doesnt achieve sufficient height to maximise flight time
How is the horizontal distance travelled by a projectile affected by the height of release
-45 degrees -> optimal angle of release
-where release height is above landing height- optimal angle of release- less than 45 degrees as projectile already has increased flight time due to increased height of release
-where release height is below landing height- optimal angle of release is more than 45 degrees as projectile needs increased flight time to overcome obstacle
What is the drag
force that opposes the direction of motion of a body through water
What is a projectile
body that is launched into the air losing contact with the ground surface, such as a discus
one factor that affects horiozntal distance travlled by a projectile
-speed of release - greater speed of release- will be thrown further
-height of release
-angle of release
What is parabolic
uniform curve symmetrical about its highest point
What is a parabolic flight path and when does it occur
flight path symmetrical about its highest point caused by dominant force of weight on a projectile
-occurs if weight is dominant force & air resistance is small
Give a sporting example of a parabolic flight path
shot put
-has high mass, travels through air at low velocity with small front cross-sectional area -> making air resistance minimal
What is a non-parabolic flight path and when does it occur
a flight path asymmetrical about its highest point caused by dominant force of air resistance on a projectile
-occurs if air resistance is dominant force and weight is very small
Give a sporting example of a non- parabolic flight path
badminton shuttle
-has low mass, travels at high velocities with uneven surface -> creates air resitance
Explain the free body diagram of a badminton shuttle in the start, mid and end of flight phases
-start: AR is much larger than W -> as velocity of shuttle = high as it leaves racket head
-mid: size of AR force has decreased as velocity of shuttle has reduced -> size of AR force causes shuttle to decelerate
-end: AR force = small, velocity of shuttle has slowed -> W force is larger than AR -> shuttle falling vertically -> non-parabolic flight
Name the 3 phases of motion within a flight path
-start of flight
-mid flight
-end of flight
What is a parallelogram of forces
diagram of the object showing the forces acting on a projctile in flight
-> e.g. air resistance (direction and size)
weight (direction and size)
Describe the 3 steps you would take to draw a parallelogram of forces
-draw free body diagram showing weight and air resistance
-add broken parallel lines to weight and air resitance arrows to create a parallelogram
-draw diagonal line from origin of weight and air resistance (centre of mass of projectile) to opposite corner of parallelogram with arrow labelled ‘resultant force’
What is an aerofoil
streamlined shape with curved upper surface & flat lower surface
-> designed to give additional lift force to body
What is the resultant force
it shows the acceleration of a projectile and the direction in which the acceleration occurs
-also shows flight path
How do you know through looking at the resultant force if the flight path is parabolic or non-parabolic
parabolic -> if resultant force = closer to weight arrow -> weight = more dominant -> parabolic flight path
non-parabolic -> if resultant force = closer to air resistance -> AR = more dominant -> non-parabolic flight path
Name characteristics of an aerofoil and how this is beneficial
-has a curved upper surface, forcing air flow to travel further distance -> moving at higher velocity
-has flat underneath surface -> air travelling at shorter distance at a lower velocity
-above the curved surface -> low-pressure zone is created
-below the flat underneath surface -> high-pressure zone is created
What is Bernoullis principle in simple terms
higher the velocity of air flow, the lower the surrounding pressure
How does an aerofoil shape give an additional lift force to a body according to Bernoullis principle
-curved upper shape -> air flow travels further -> moves higher velocity -> low pressure zones created
-flat underneath -> air travels shorter -> moves at lower velocity -> high pressure zone created
THEREFORE:
-as velocity increases, pressure decreases
-as fluids move from area of high pressure -> low pressure -> pressure gradient forms -> creating additional lift force
-lift force ^ time projectile hangs in air -> ^ flight path, horiziotal distance -> ^ results
What is lift force
additional force created by pressure gradient forming on opposing surfaces of an aerofoil moving through a fluid
What is angle of attack
most favourable angle of release for projectile to optimise lift force
Give an example of a sport which adopts Bernoullis principle
ski jumper
Explain using a sporting example Bernoullis downward lift force principle
-front wing funnels air down through narrow space underneath cars chassis
-soiler acts as an inverted aerofoil -> forces air underneath to travel further distance
-this ^ air velocity unerneath car -> creating areas of low pressure
-pressure gradient is formed; downward lift force = created
-results in ^ grip & friction around corners at high speeds
How is spin created
created by applying an external force outside centre of mass
Name the 4 types of spin, explain the force applied and the result of this force
topspin -> eccentric force applied above COM, projectile spins downwards around transverse axis
backspin -> eccentric force applied below COM, projectile spins upwards around transverse axis
sidespin hook -> eccentric force applied right of COM, projectile spins left around longitudinal axis
sidespin slice -> eccentric force applied left of COM, projectile spins right around longitudinal axis
What is a magnus force
force created from a pressure gradient on opposing surfaces of a spinning body moving through the air
What magnus force does topspin create and how does this effect its flightpath
topspin creates downward magnus force
-> shortening flight path
What magnus force does backspin create and how does this effect its flightpath
backspin creates upward magnus force
-> lengthening flight path
What magnus force does sidespin rotation create and how does this effect its flightpath
sidespin rotation creates magnus force to the right and left
-> swerving projectile right (slice) & left (hook)
What is the magnus effect
creation of an additional magnus force on spinning projectile which deviates from the flight path
What is a hook
type of sidespin used to deviate projectiles flight path to left
What is a slice
type of sidespin used to deviate projectiles flight path to right
Explain how topspin occurs in tennis
upper surface of ball rotates towards oncoming air flow -> oppoising motion, decreasing velocity of air flow -> creating high pressure zone
-lower surface of ball rotates in same direction as air flow, increasing velocity of air flow -> creating low pressure zone
-pressure gradient forms, additional magnus force is created downwards
-downward magnus force adds weight to projectile
-projectile dips in flight -> less time in air -> flight path shortens
Name 3 reasons as to why spin is useful in table tennis and tennis
-gives ball stability in flight
-can confuse opposition
-topspin shortnes flight path -> allowing ball to still be hit hard but still land in court
hook spin description
slice spin dexciription
