Biomechanical Movement: The Bernoulli Principle

Question 1

Who is Daniel Bernoulli and what is his principle?

Answer 1

• His theory was tht an increase in the speed of a fluid occurs as a result of a decrease in pressure

Question 2

Example: Discus

Answer 2

• When a discus is thrown, it experiences upward lift force
• Upward lift enaables the discus to stay in the air longer
• This will increase the horizontal displacement

Question 3

What is the lift force?

Answer 3

• Causes a body to move perpendicular to the direction of travel

Question 4

Direction of airflow?

Answer 4

• Air travels further the top.
• This creates high velocity and low pressure.
• Air has less distance to travel underneath
• This creates low velocity and high pressure

Question 5

Changing air pressures?

Answer 5

• Air that travels fast, has low pressure.
• Air that travels slow, has high pressure
• Air always moves from an area of hgih pressure to low pressure
• This creates an upward lift force through the object meaning the discus stays in the air longer.
• Greater horizontal displacement is achieved

Question 6

What is the angle of attack?

Answer 6

• A discus will have an angle of attack to the direction of motion
• The optimum angle for relewase of a discus is 25-40 degrees
• If the release is too great, lift force will reduce, and drag force will increase
• The docus will stall and not travel far.
• It has an aerofoil shape
• Air has to travel further over the top of the discus
• This creates low pressure area on top of the dicus called the Bernoulli Principle
• Air tries to move from a high pressure to low
• Makes flight path non parabolic/asymmetrical
• Discus travels furhter

Question 7

What is downward lift?

Answer 7

• Lift forces dont always work in an upward direction
• Bernoulli principle can also be used to describe downward lift
• By pushing the object/body in to the ground, the greater the frictional forces created

Question 8

What is the purpose of a spoiler on a racecar?

Answer 8

• Due to the angle of the spoiler, air travelling over the top has a shorter distance.
• The air travels at a slower velocity.
• The air above has a high pressure while air travelling under has a longer distance.
• The air below travels at a greater velocity and a low pressure.

Question 9

Downward lift applied to cycling

Answer 9

• The airfoil shape of a cyclist helmet and their crouched body position, means that air travelling over the top has a shorter distance to travel that the air underneath.
• Air above the cyclist travels at a slower velocity and higher pressure
• Air below the cyclist travels at higher velocity and lower pressure
• The pressure gradient created enables air to travel from high pressure to low pressure creating a downward lift force