Lectures 19-20 Fluid Dynamics

Question 1

Definition of buoyancy

Answer 1

A solid immerses in a fluid will be buoyed up by a force that is equal to the weight of the fluid displaced

Question 2

Equation for density

Answer 2

Density = mass/volume

Question 3

Units for density

Answer 3

Kg/m(cubed)

Question 4

Look at different density’s of water

Answer 4

Slide 8, lecture 19

Question 5

What are some types of drag (when swimming)

Answer 5

Surface or skin (friction) drag

Form or pressure drag

Wave drag

Question 6

Look at what different symbols mean

Answer 6

Slide 14, lecture 19

Question 7

Different types of flows

Answer 7

Slide 15, lecture 19

Question 8

What is the Bernoulli effect?

Answer 8

When flow lines in a fluid get close together, their velocity increases and the pressure drops

(Diagram on slide 4, lecture 20 explains)

Question 9

Look at Magnus effect in PE book

Answer 9

Pages 105/106

Question 10

Equation for Reynolds number (check if you have to learn this on recap recording)

Answer 10

Slide 14, lecture 20

Question 11

What is the equation for drag?

Answer 11

F(drag) = 1/2 C(drag). A. (rho). v(squared)

Question 12

What does F(drag) stand for in the drag equation?

Answer 12

Force due to drag

Question 13

What does C(drag) stand for in the drag equation?

Answer 13

Coefficient of drag

Question 14

What does A stand for in the drag equation?

Answer 14

Surface area

Question 15

What does (rho) stand for in the drag equation?

Answer 15

Density (or viscosity)

Question 16

What does v(squared) stand for in the drag equation?

Answer 16

Relative velocity

Question 17

What is laminar flow?

Answer 17

Where there is a nice separation and return back of particles and the flow of air

Question 18

When does laminar flow occur?

Answer 18

At very low speeds

Question 19

What happens to the movement of air particles around an object when the air starts to move faster?

Answer 19

You have a separation of the flow but the particles do not come back together because the air flow is moving so fast

Question 20

When air particles start to not rejoin each other after they pass an object, what does this cause?

Answer 20

A low pressure, turbulent wake behind the object

Question 21

Why is having low pressure behind you a negative thing?

Answer 21

Because if you have low pressure behind you, it acts to drag you back

Question 22

Equation for Reynolds number?

Answer 22

Reynolds number = density x size x viscosity x relative velocity

Question 23

At greater speeds what happens to drag on a rough ball?

Answer 23

It (in the case of that video) has less drag than the smooth ball

Question 24

What happens at lower speeds in terms of drag on a rough ball and smooth ball of equal sizes?

Answer 24

There is less drag on the smooth ball

Question 25

Why does a golf ball, when hit very hard, have less drag than a smooth ball?

Answer 25

Because of the dimples on the surface

Question 26

For any given force, an eccentric contraction requires less what than a concentric contraction? What is a benefit of this?

Answer 26

Requires less activity
Requires less o2 uptake and energy intake

Can go longer before fatigue