Projectile motion Flashcards
What is the definition of fluid mechanics?
The study of forces acting upon a body travelling through water/air
What is air resistance?
Force opposing the direction of motion of an airborne object
What is drag?
Force opposing the direction of motion of a body travelling through a fluid
What factors affect air resistance/drag?
Velocity Frontal cross sectional area Streamlining/shape Surface characteristics Temperature Altitude/air density Mass
How does velocity affect air resistance/drag?
The higher the velocity, the higher the AR/drag
How does frontal cross sectional area affect air resistance/drag?
The smaller the frontal cross sectional area the smaller the AR/drag
How does streamlining/shape affect air resistance/drag?
The more streamlined, the less AR/drag
The teardrop shape is the most streamlined
How does surface characteristics affect air resistance/drag?
The smoother the surface, the less AR/drag
How does temperature affect air resistance/drag?
The lower the temperature the more AR/drag as density of air increases
How does altitude/air density affect air resistance/drag?
The lower the air density/higher the altitude the less AR/Drag
How does mass affect air resistance/drag?
The higher the mass, the more AR/drag
Describe the speedo LZR swimming suite/its restrictions
Full body suite that is hydrophobic, reduces drag so increases velocity.
Must be above knee and below belly button (men)
Why was the spyder tripwire suite banned from skiing?
Reduce AR up to 40%
Banned because gave some performers an unfair advantage
Thin wire pulls pads in to reduce surface area and therefore, AR. Can still have ones that reduce AR by 20%.
Definition of projectile motion?
Motion of a body through the air following a curved flight path.
What is the definition of a projectile?
A body launched through the air and losing contact with a contact/ground surface.
What is the definition of a parabola?
A uniform curve symmetrical about its highest point
What force is dominant when the flight path is a true parabola?
Weight
What force is dominant when the flight path is non-parabolic?
Air resistance
How does air resistance affect the flight path of an object?
The greater the effect of AR the greater the projectile will deviate from a true parabolic flight path.
Why does a shot put have a parabolic flight path?
Weight is dominant.
Shot has a large mass.
Travels at a low velocity and has a smooth and small frontal cross sectional area so a small AR.
Why does a shuttlecock have a non parabolic flight path?
AR is the dominant force.
Shuttle has a small mass.
Travels at a high velocity and has a rough/large frontal cross sectional area so has a large AR
What affects the flight path of a projectile?
Speed of release
Angle of release
Height of release
Aerodynamic factors (Bernoulli/Magnus)
What is the primary factor affecting the horizontal distance travelled?
Speed of release
Which one of Newton’s laws links to speed of release?
Second law of acceleration
How do you link Newton’s second law to a projectile?
The greater the force applied to the projectile, the greater the change in momentum and acceleration of the projectile into the air at the point of release.
As acceleration of the projectile increases what happens to horizontal distance?
It increases.
Therefore, there is a greater importance for upper body strength to enable throwing related sports.
What is the optimum angle of release for projectiles released from the ground?
45 degrees
What happens if a projectile is released at less than 45 degrees from the ground?
Does not achieve sufficient height to maximise flight path time. Decrease height = decrease flight time = decrease distance.
What happens if a projectile is release at more than 45 degrees from the ground?
Reaches peak height too quickly and rapidly returns to ground. Increase height, increase flight time but decrease distance.
What happens if a projectile is released at 90 degrees?
Body travels vertically upwards and straight down (0 meters)
When is 45 degrees the optimal release angle?
When the release height is the same as the landing height eg long jump/chip shit in golf
When is a release height of less than 45 degrees optimal?
When release height is above the landing height (Positive release angle) eg shot put
When is a release height of more than 45 degrees optimal?
When the release height is below the landing height (negative release angle) eg golf bunker/basketball shot
What is the Bernoulli principle?
The theory of how an additional lift force is created during flight based on the shape of a projectile
What is the definition of lift force?
Additional force created from pressure gradients forming on opposite surfaces of an aerofoil moving through fluid.
What direction does lift force act in?
Perpendicular to the direction of motion
What is the effect of lift force on a projectile?
Increases potential flight time of a projectile and therefore the horizontal distance travelled
What is the pressure when the velocity is high?
Low
What is the pressure when the velocity is low?
High
What affects the velocity of air passing an aerofoil?
The further the air has to travel, the faster the air must travel.
How do you draw an air flow diagram?
Must show DOM arrow. 3 air flow lines above and below the projectile.
Airflow opposes DOM.
Closer together airflow lines = higher velocity of air.
Label velocity and pressure, above and below projectile.
Show lift force acting from centre of mass.
What is the angle of attack?
The most favourable angle of release, of a projectile, to optimise lift force to increase flight time/horizontal distance.
What is the definition of an aerofoil shape?
A streamlined shape with a curved upper surface and a flat lower surface.
What happens if an aerofoil is inverted?
The Bernoulli lift force acts in a downwards direction
What is the definition of an inverted aerofoil shape?
A streamlined shape with a curved lower surface and flatter upper surface
What is the affect of downwards lift force on F1 cars?
Increased grip when cornering at high speeds
What do the front wings do on an F1 car?
Funnel air downwards, increasing distance for air flow, increasing air flow velocity.
What does the rear spoiler do on F1 cars?
Acts as an inverted aerofoil, decreases air velocity above which increases pressure.
Increases air velocity below which decreases pressure.
What does a cyclists helmet, high seat and low handlebars create?
A flatter upper body surface to create a teardrop shape
How does the teardrop shape help a cyclist?
It is a streamlined shape that reduces the frontal cross sectional area/air resistance and creates additional lift force
How does increasing lift force help a cyclist?
Additional downwards force, increased effect of weight/reaction force with the track. Increases friction so both grip and velocity are maximized.
What is the definition of the Magnus effect?
When a lift force is applied to a spinning projectile
Causes the projectile to deviate from the original flight path.
What is the definition of Magnus force?
Force created from high to low pressure gradients on opposing surfaces of a spinning projectile.
What is the affect of the Magnus force?
Causes a spinning projectile to deviate away from its expected flight path
What spin is from side views?
Topspin
Backspin
What spin is from a top view?
Right side spin - slice
Left sidespin - hook
Where is the eccentric force applied on each type of spin?
Topspin - above COM
Backspin - Below COM
Slice - Left of COM (spins right)
Hook - Right of COM (Spins left)
What is the direction of spin/axis of rotation for topspin?
Spins downwards
Around transverse axis
What is the direction of spin/axis of rotation for backspin?
Spins upwards
Around transverse axis
What is the direction of spin/axis of rotation for a slice?
Spins right
Around longitudinal axis
What is the direction of spin/axis of rotation for a hook?
Spins left
Around longitudinal axis
What is the effect of topspin on flight path?
Shortens flight path
What is the effect of backspin on flight path?
Lengthens flight path
What is the effect of a slice on flight path?
Swerves to the right
What is the effect of a hook on flight path?
Swerves to the left
Describe the upper surface in a ball with topspin?
Rotates opposite to airflow, decreasing velocity to create a high pressure area
Describe the lower surface in a ball with topspin?
Rotates in same direction as airflow, increases velocity creating an area of low pressure
How does a ball with topspin create a Magnus force?
Creates an area of high/low pressure. Magnus force acts downwards
What is the affect of the Magnus force in a ball with topspin?
Downwards force increases weight/effect of gravity so projectile dips in flight and reduces flight path/distance.
What is the advantage of topspin?
Dips so can be hit with a greater velocity and it will remain in bounds.
Increases stability in flight.
What is the checklist for drawing an airflow diagram?
State spin/angle of view
Draw DOM arrow
Draw direction of spin arrows
Draw airflow opposite to DOM (3 lines each side)
Label area of high/low velocity
Label area of low/high pressure
Draw Magnus force from COM (high-low pressure)
Link to affect - performance/flight path if appropriate
What are the advantages of hitting a ball with backspin?
Increased friction on landing, decelerates and increases bounce height on landing
