fluid mechanics

Question 1

lift force

Answer 1

causes a body to move perpendicular to the direction of travel

Question 2

drag force

Answer 2

a force that acts in opposition to motion

Question 3

bernoulli principle

Answer 3

where air molecules exert less pressure the faster they travel and more pressure when they travel slower

Question 4

angle of attack

Answer 4

the tilt of a projectile relative to the air flow

Question 5

what does a discus experience when it is thrown?

Answer 5

an upward lift force during flight

Question 6

what does a lift force on a discus enable?

Answer 6

a lift force enables the discus to stay in the air for longer, therefore increasing the horizontal distance is travels

Question 7

what happens with the more lift a projectile has during flight?

Answer 7

the longer it will stay in the air and the further the horizontal displacement it will travel

Question 8

how is lift achieved

Answer 8

when different air pressures act on an object

Question 9

what does air that travel fast have

Answer 9

lower pressure

Question 10

what does air that travel slow have?

Answer 10

higher pressure

Question 11

what does the angle of attack do?

Answer 11

it changes the flow of air around the discuss so the air travels over the top of the discuss has to travel a longer distance than the air underneath

Question 12

what does the angle of attack on a discus result in?

Answer 12

the air above the dicus travelling at a faster velocity, which therefore creates a lower pressure

Question 13

what does a lower pressure above the dicus create?

Answer 13

the lower pressure above the dicus creates an upward lift force and allows the dicus to stay in the air for longer, resulting in a greater horizontal distance

Question 14

what happens if the angle of attack is too great?

Answer 14

then the lift is reduced and drag increases, causing the discus to stall

Question 15

optimum angle of attack for a discus

Answer 15

20-40 degrees

Question 16

what are examples of downward lift force angle of attack?

Answer 16

• speed skiers
• cyclists
• racing cars

Question 17

what do F1 cars have causing a downward lift force?

Answer 17

spoilers angled so that the lift force can act in a downward direction to push the car into the track

Question 18

how do spoilers create a downward lift force?

Answer 18

because the air that travels over the top of the car travels a shorter distance than the air underneath, due to the angle of the spoiler

Question 19

how do cyclists’ body positions benefit them?

Answer 19

because it means that air that travels over the top of the cyclist has to travel a shorter distance than the air underneath

Question 20

what does the air travelling over a shorter distance over the top of a cyclist result in?

Answer 20

the air above the cyclist travelling at a slower velocity which therefore creates a higher pressure

Question 21

what does a higher pressure above the cyclist create?

Answer 21

a downward lift force and allows the tyres of the bike to maintain a firm grip on the track

Question 22

how does a downward lift force benefit speed skiers?

Answer 22

because more downward acting lift means more force which melts the snow for a better friction-free surface