Fluid Mechanics and Projectile Motion

Question 1

What is fluid mechanics?

Answer 1

The study of the forces acting on a body travelling through the air or water

Question 2

What are the 4 main factors that affect the magnitude of air resistance and drag on a body?

Answer 2

• Velocity
• Cross sectional area
• Streamlining
• Surface characteristics

Question 3

What is projectile motion?

Answer 3

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

Question 4

What is a projectile?

Answer 4

A body that is launched into the air losing contact with the ground surface, such as a discuss or long jumper

Question 5

What 4 factors affect the distance travelled by a projectile?

Answer 5

• Speed of release
• Angle of release
• Height of release
• Aerodynamic factors (Bernoulli and Magnus)

Question 6

How does SPEED OF RELEASE affect the distance?

Answer 6

The greater the outgoing speed of the projectile, the further it will travel.

Question 7

How does ANGLE OF RELEASE affect the distance?

Answer 7

90 degrees - projectile will accelerate vertically upwards and come straight back down, travelling 0m

45 degrees - Optimal angles to maximise horizolntal distance

> 45 degrees - The projectile reaches peak height too quickly and rapidly returns to the ground

< 45 degrees - The projectile does not achieve sufficient height to maximise flight time

Question 8

How does HEIGHT OF RELEASE affect the distance?

Answer 8

• If release height is above the landing height, the optimal angle of release is <45 because the projectile already has an increased flight time due to the increased height
• If the release height is lower than the landing height, the optimal angle of release is >45 as projectile needs an increased flight time to overcome the obsticle

Question 9

What are the 2 types of flight path?

Answer 9

• Parabolic flight path
• Non-Parabolic flight path

Question 10

What is a parabolic flight path?

Answer 10

If the weight is the dominant force and air resistance is very small, a parabolic flight path occurs.
- It has a symmetrical shape about its highest point

Question 11

What is a non-parabolic flight path?

Answer 11

A flight path asymmetrical about its highest point caused by the dominant force of air resistance on the projectile

Question 12

What are the 3 phases of motion wihin a flight path, and what do air resistance and weight look like at these?

Answer 12

Phases:
- Start of flight
- Mid flight
- End of flight

Over these phases weight force does not change, whereas air resistance may be dependent on the velocity of the moving projectile

Question 13

What is meant by ‘Parallelogram of forces’?

Answer 13

A parallelogram illustrationg the theory that a diagonal drawn from the point where forces are represented in size and direction shows the resultant force acting on the projectile

Question 14

What is the resultant force?

Answer 14

The sum of all forces acting on a body or the net force acting on the projectile

Question 15

What is Bernoulli’s principle?

Answer 15

The theory of how an additional lift force can be created during flight based on the shape of a projectile.

Question 16

How does air move around the aerofoil?

Answer 16

• The curved upper surface forces air flow to travel a further distance and therefore move at a higher velocity
• The flat underneath surface allows air to flow a shorter distance and therefore at a comparatively lower velocity

Question 17

What is pressure like around the aerofoil?

Answer 17

As velocity increases, pressure decreases. A low pressure zone is created above the curved, upper surface. A high pressure zone is created below the flat, underneath surface.

Question 18

What is the optimal angle of attack?

Answer 18

17 degrees

Question 19

How is lift force created?

Answer 19

As all fluids move from an area of high to low pressure, a pressure gradient forms, creating an additional lift force

Question 20

What sports utilise downward lift force?

Answer 20

• Formula 1
• Track cycling

Question 21

What is the Magnus effect?

Answer 21

The creation of an additional Magnus force on a spinning projectile which deviates from the flight path

Question 22

What is Magnus force?

Answer 22

A force created from a pressure gradient on opposing surfaces of a spinning body moving through the air

Question 23

What are the 4 types of spin?

Answer 23

• Topspin
• Backspin
• Hook sidespin (spins left)
• Slice sidespin (spins right)

Question 24

What type of flight path does Magnus force create?

Answer 24

Non-parabolic flight paths