Fluid mechanics- drag

Question 1

What is fluid mechanics?

Answer 1

• Fluid mechanics is the study of fluids (gases and liquids) and how forces affect them.
• Fluid dynamics is a part of fluid mechanics.

Question 2

Fluid forces

Answer 2

Fluid dynamics are affected by fluid forces.
The two fluid forces are:
- Drag
- Lift

*These forces play a massive role in certain sports such as cycling, swimming and sprinting.
- They also affect certain projectiles such as balls, discus’s and javelins.

Question 3

Drag force

Answer 3

• A drag force is a resistance force which slows a body or object down.
• It acts in direct opposition to movement.
• It has a negative effect on velocity.

Question 4

What are the 2 types of drag?

Answer 4

1. Form drag
2. Surface drag

Question 5

What is surface drag?

Answer 5

(Skin drag)
- Caused by friction when the fluid environment passes over the surface of an object or the body.

Question 6

What is form drag?

Answer 6

(Shape drag)
- Basically how the size and shape of an object/body can affect how water/ air pass over it.
- Forces that affect the leading edge increase drag.
- Forces that affect the trailing edge reduce drag.
- Altering a body/ object so that it passes through the air and water more efficiently is called streamlining.

Question 7

‘Drafting’ in cycling

Answer 7

• A large from drag also offers less turbulent air for anything that follows.
• This is called a slipstream.

How does this work in cycling?
- 15-30cm
- 30%

Question 8

Factors that increase and reduce drag

Answer 8

1. The velocity of the moving object.
2. The cross sectional area of the moving body.
3. The shape and surface characteristics of the moving body.