fluid mechanics

Question 1

fluid mechanics

Answer 1

• the study of an object or the human body through liquid or gas
• E.G swimmers travel through water and a tennis ball through air - both slowed down by friction and drag
• look at the effect of an upward lift force on the discus and the downward lift force on speed skiers , cyclists and racing cars

Question 2

dynamic fluid force

Answer 2

• fluid dynamics is concerned with the movement of liquids and gases
• drag and lift are dynamic fluid forces - the effect a variety of sports
• any projectiles such as a ball, discuss and javelin will experience drag and lift force

Question 3

drag force

Answer 3

• slows down something
• is a resistance force caused by the morion of an object travelling through a fluid
• acts in the opposite direction of motion and therefore has a negative effect on velocity
  drag force is produced from air resistance and friction
• E.G a cyclist will constantly try to reduce drag ti increase velocity

Question 4

two types of drag force

Answer 4

• surface drag
• form drag

Question 5

surface drug

Answer 5

• relates to frcition between the surface on an object and fluid environment
• it is sometimes called skin drag
• E.G swimmers will wear specialist smooth clothing and shave body hair to reduce surface drag

Question 6

form drag

Answer 6

• relates to the impact of fluid on an object
• referred to as shape draft
• the force affecting the leading edge of an object increase form drag and the force affecting trailing edge reduce from drag
• form drag relates to streamlining - A swimmer needs to create the thinnest and straightest form moving though water to reduce drag

Question 7

form drag analagy

Answer 7

• a large form drag offers a less turbulent air for anything that is follwoing
• for example in a slipstream
  eg
• a cyclist will use another riders slipstream (known as drafting)
• as the wind hits the front cyclist, it goes around the sides and the cyclist behind uses the air pockets that has been created
• for it to work a cyclist has to follow very closly to the bike infront (15-30cm) - can save up to 30% energy

Question 8

factors that increase and reduce drag

factors that increase and reduce drag

Answer 8

• the velocity of the moving body
• the cross sectional area of the moving body
• the shape and surface characteristics of a body

Question 9

the velocity of the moving body

factors that increase and reduce drag

Answer 9

• the greater the velocity of a body through a fluid, the greater the drag force
• a sport that experiences greater air resistance, the greater the drag will be
• E.G a racing car , sprinter or cyclists

Question 10

the cross sectional area of the moving body

factors that increase and reduce drag

Answer 10

• can increase and decrease drag
• the larger the cross sectional area of a body the larger the drag
• the smaller the cross sectional area of a body the smaller the drag
• in sports reducing the effects of drag can be crucial for success

Question 11

the shape and surface characteristics of a body

factors that increase and reduce drag

Answer 11

• a more streamline, aerodynamic shape reduces drag
• clothing to help streamline and achive those marginal gains
• helmets, bodysuits , shaving , swim caps
• the shape of badminton shuttle and the feathers result in a much larger air resistance to reduce speed rapidly

Question 12

bernoulli principle

Answer 12

• when a discus is thrown , it experiences upwards lift force during flight
• a lift force enables the discuss to stay in the air longer, therefore increasing the hosizontal distance it dravels
• lift is achieved when air pressure acts on an object
• air that travels faster has a lower pressure than air that travels slower

Question 13

discuss - bernoulli principle

Answer 13

• angle of attack is important
• the angle changes the flow of air around the discuss so the air that travels over the top of the discus has to travel longer distance than the air underneath
• this results in the air above the discuss travleing at a fast velocity which therefore creates a lower pressure
• the air that travels below the discuss has less distance to cover so travels at a slower velcoity - which creates higher pressure

Question 14

upwards force

Answer 14

• the higher the pressure below the discus creates an upwards lift force and allows the discuss to stay in the air for linger - resulting in a greater horizontal distance
• if the angle of attak is too great , the lift is reduced and drag increases, causin the discus to stall
• the optimum angle of attack between 25 and 45 degrees for discuss

Question 15

downward lift

Answer 15

• required by speed skiers, cyclists and racing cars
• these sports equire the body to be pushed down into the ground so a greater frictional force is created
• in f1 the cars spoiler is angle so the lift force can act in a downward dircetion to push the car into the track
• this happens bc the air that travels over the top of the car, travels a further distance than underneath
• the air above the car travels at a slower velocity at a higher pressure