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MS CAMPBELL PE > YR2 FLUID MECHANICS > Flashcards

YR2 FLUID MECHANICS Flashcards

1
Q

What is Air Resistance?

A

The force that opposes the direction of motion of a body through air

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2
Q

What is Drag ?

A

The force that opposes the direction of motion of a body through water

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3
Q

What are the 4 ways you can lower magnitude?

A

Velocity
Frontal Cross sectional area
Streamlining + shape
Surface Characteristics

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4
Q

Describe how Velocity can lower magnitude?

A

The faster a body is traveling the greater the force, although realistically you would not want to decrease velocity as you would lose the race

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5
Q

Describe how Frontal Cross sectional area can lower magnitude?

A

The larger the the cross sectional area the greater the force opposing motion

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6
Q

Describe how Streamlining + shape can lower magnitude?

A

The more streamlined or aerodynamic the shape the lower the opposing force. Aerofoil shape is commonly used

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7
Q

Describe how Surface Characteristics can lower magnitude?

A

The smoother the surface the lower the opposing force

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8
Q

Using Cycling - explain how you can lower magnitude ?

A

Frontal Cross Sectional Area -
Shoulders forward high saddle position (tilt the body)
Narrow Handlebars
Arms tucked in

Streamlining + Shape -
Body Angle
Aerodynamic Helmets

Surface Characteristics -
Smooth glossy helmets
Shaved body
Tight lycra clothing

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9
Q

What is Projectile motion?

How can it be shown?

A

The movement of a body through the air following a curved flight path under the force of gravity

The flight path of a projectile can be shown on a simple graph of height Vs distance

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10
Q

What are the 4 Factors that affect the length of the parabola due to release?

A

Speed of release
Angle of release
Height of release
Aerodynamic factors

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11
Q

How does Speed of release affect the length of the parabola due to release?

A

This has the largest effect, due to newton’s second law. The faster the speed of release the longer the parabola.

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12
Q

How does Angle of release affect the length of the parabola due to release?

A

90 degree would travel 0m, 45 is the optimum lower than that not enough height is generated and above that the peak of the parabola is reached to early and it plummets to the ground.

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13
Q

How does Height of release affect the length of the parabola due to release?

A

If the projectiles landing height is the same as the height it was thrown at then 45 degrees is optimal but if it has a higher throwing height the angle is reduced and the opposite

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14
Q

How does Aerodynamic factors affect the length of the parabola due to release?

A

Magnus and Bernoulli effects

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15
Q

What is the Flight Path?

A

The way in which a projectile travels is usually in the shape of a parabola but it can be deviated from for different reasons

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16
Q

What happens if the weight of the projectile is high?

A

If the weight of the projectile is high then the effect of the air resistance is very small so a normal parabola occurs

17
Q

What happens if the weight of the projectile is high? (SPORTING EXAMPLE)

A

e.g. Shot put (heavy, low velocities, small surface area and smooth)

18
Q

What happens if the weight of the projectile is low?

A

If the weight of the projectile is low then the effect of the air resistance is the dominant force so a non-parabolic curve occurs

19
Q

What happens if the weight of the projectile is low? ( SPORTING EXAMPLE)

A

e.g. Shuttlecock (light, high velocity’s, large surface area and rough)

20
Q

What are the 4 tips for free body diagrams?

A

Weight acts downwards
Always shoe direction of motion
Length of the arrow shows the size of the force
Weight (W) and Air resistance (AR) should act from the center of mass

21
Q

How are PARALLELOGRAM OF FORCES created?

A

This is created by drawing a free body diagram and then drawing parallel lines to AR and W, this creates a parallelogram and then you draw in the resultant force from the center of mass to the diagonally opposite corner.

22
Q

What is Bernoulli’s Principle?

A

Bernoulli’s realised a lift force could be generated on a projectile

It is used to extend the
parabola of flight and
therefore is helpful in
sport.

23
Q

How would you Draw an airflow diagram which represents a javelin in flight?

A

Draw picture and lines around the javelin.
Draw in the direction of motion.
Draw the forces (weight and air resistance)
Draw the lift force.
The javelin is release with an angle of attack.
Travels in an aerofoil shape.
Air under the javelin travels less distance and therefore travels slower at a higher pressure.
The air above travels further and faster and therefore at a lower pressure.
The pressure differential causes at uplifting force.
This extends the parabolic flight path (it stays in air for longer).

24
Q

What is the Magnus effect?

A

The effect of spin on the flight path of a projectile e.g. tennis ball.

It uses Bernoulli’s principle but to create spin rather than a lift force.

25
Q

What does it mean if the spin opposes the direction of airflow?

A

If the spin opposes the direction of airflow
then and the air velocity is decreased,
this causes a creation of an area of high
air pressure to be formed.

This then works to Bernoulli’s principle creating a lift force
(in the case of back spin)

26
Q

Explain how a topspin works?

A

Attacking flight path.
Travels high and fast.
Dips in flight and pulls down before it bounces out.
Flight path shortened.
Non parabolic.
Pushes the opponent deeper in the court.
Magnus force down.
Negative-travels fast so if you hit it fast at opponent it will come back at you just as fast (in tennis)

27
Q

Explain how a backspin works?

A

The ball spins backwards.
Ball travels slowly, allows the player to recover.
Defensive shot-hangs in the air for longer
Magnus force is up.
This extends and lengthens flight.
Non parabolic pathway.
Can be used for a drop shot.
Brings a player forward who likes to play deep.
Negative-ball can go long because of an elongated flight path.

28
Q

What is the difference between a topspin and backspin?

A

Top spin:
Creates a downward Magnus force
Shortens the parabola
Increases the speed of the bounce and makes the bounce angle smaller
The spin does not appose the direction of motion

Back spin:
 Creates a lift Magnus force
 Extends the parabola
Decreases the speed of the bounce and makes the bounce angle larger
The spin apposes the direction of motion
29
Q

What is the difference between a slice and hook?

A

Hook - The swerving of a projectile to the left
Slice - The swerving of a projectile to the right

Both look to create a Magnus force to change the flight path, it is used in golf to avoid trees to get to the fairway or in football to avoid a wall at a free kick

MS CAMPBELL PE (8 decks)

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