Projectile motion

define projectile motion + projectile

projectile motion - movement of body through air following curved flight path under force of gravity

projectile - body launched into air losing contact with ground

explain the factors affecting horizontal distance travelled by a projectile

speed of release - due to N2 the greater the speed of projectile the further it will travel

angle of release - 45^o is usually optimal

height of release - 45^o is optimal if release + landing height are equal, if release is higher than landing optimal angle is less than 45, if release is lower than landing more than 45

aerodynamic factors - Bernoulli + Magnus effects

describe the different flight paths, how they occur + give an example of each

parabolic - uniform curve symmetrical about its highest point, weight is the dominant force, e.g. shot put

non-parabolic - curve asymmetrical about its highest point, air resistance is dominant force, e.g. shuttlecock, discus

define Bernoulli principle

creation of additional lift force on projectile in air

describe aerofoil shape

curved upper surface + flat underside

how is the Bernoulli effect generated

air on top of aerofoil has a further distance to travel so gain momentum

so air velocity is high above aerofoil

air underneath has shorter distance to travel so less momentum

so air velocity low under aerofoil

as velocity increases, pressure decreases

fluids move from high to low pressure so pressure gradient forms

creates additional lift force so projectile stays in air longer

define angle of attack + state the optimal to maximise lift

most favourable angle of release for a projectile to optimise lift force due to Bernoulli principle

optimal angle of attack is 17^o

explain how the Bernoulli principle can work downwards + give an exmaple of a use

reverse aerofoil shape causes low air velocity + so high pressure above

+ high air velocity + so low air pressure above

gases move from high to low pressure

so downward Bernoulli effect generated

e.g. spoiler of F1 car

define Magnus force

force created from pressure gradient on opposing surfaces of spinning body moving through air

describe how each type of force is generated + how projectile spins

topspin - eccentric force applied above COM, ball spins downwards

backspin - eccentric force applied below COM, ball spins upwards

hook - eccentric force applied to right of COM, ball spins to left

slice - eccentric force applied to left of COM, ball spins to right

describe how topspin in generated

eccentric force applied above COM
air velocity low above ball (as air travels in same direction as ball spins) so pressure high

air velocity high above ball so pressure low

gases move from high to low pressure

so creates downwards Magnus force

advantages of topspin (5)

shorter flight path due to acceleration on ball

ball kicks when it hits ground due to friction acting with direction of travel

forces opponent back in tennis/table tennis

makes ball dip when striking ball in football

ball kicks up in cricket bowling (“flipper”)

disadvantages of topspin (2)

difficult to control (hit net in tennis/wall in football)

lose distance in golf

advantages of backspin (5)

longer flight path to allow recovery in tennis/table tennis

low bounce due to friction acting in opposite direction to direction of travel

further distance in golf/football

can make ball hang in basketball

keep ball low in cricket

disadvantage of backspin

allow opportunity for opponent to attack (slower)

advantages of sidespin (4)

unpredictable for opponent (especially in cricket)

manipulate flight path of ball around object (e.g. golfer or footballer around wall)

flight path deviates from origin

friction acts in sideways motion

disadvantage of sidespin

difficult to control