fluid mechanics Flashcards
lift force
causes a body to move perpendicular to the direction of travel
drag force
a force that acts in opposition to motion
bernoulli principle
where air molecules exert less pressure the faster they travel and more pressure when they travel slower
angle of attack
the tilt of a projectile relative to the air flow
what does a discus experience when it is thrown?
an upward lift force during flight
what does a lift force on a discus enable?
a lift force enables the discus to stay in the air for longer, therefore increasing the horizontal distance is travels
what happens with the more lift a projectile has during flight?
the longer it will stay in the air and the further the horizontal displacement it will travel
how is lift achieved
when different air pressures act on an object
what does air that travel fast have
lower pressure
what does air that travel slow have?
higher pressure
what does the angle of attack do?
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
what does the angle of attack on a discus result in?
the air above the dicus travelling at a faster velocity, which therefore creates a lower pressure
what does a lower pressure above the dicus create?
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
what happens if the angle of attack is too great?
then the lift is reduced and drag increases, causing the discus to stall
optimum angle of attack for a discus
20-40 degrees
what are examples of downward lift force angle of attack?
- speed skiers
- cyclists
- racing cars
what do F1 cars have causing a downward lift force?
spoilers angled so that the lift force can act in a downward direction to push the car into the track
how do spoilers create a downward lift force?
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
how do cyclists’ body positions benefit them?
because it means that air that travels over the top of the cyclist has to travel a shorter distance than the air underneath
what does the air travelling over a shorter distance over the top of a cyclist result in?
the air above the cyclist travelling at a slower velocity which therefore creates a higher pressure
what does a higher pressure above the cyclist create?
a downward lift force and allows the tyres of the bike to maintain a firm grip on the track
how does a downward lift force benefit speed skiers?
because more downward acting lift means more force which melts the snow for a better friction-free surface
