Every Conservation Part 2

Question 1

Why can pressure be negative?

Answer 1

• At these points you need a high pressure at the bottom to move water up. Pressure at the highest points is negative. Corresponds to the pressure you need to get through the range of heights

Question 2

What does it mean when pressure is negative?

Answer 2

Negative pressure in pipe fluid flow refers to a situation where the pressure in a section of the pipe is lower than the surrounding atmospheric pressure

Question 3

What happens if pressure becomes too negative?

Answer 3

If pressure becomes too negative you end up with some backflow → Pressure can never become so negative that it reaches absolute zero i.e., a vacuum

Question 4

Why does a syphon have a limit on how far you can push water up?

Answer 4

So pressure doesnt become too negative

Question 5

What is the datum?

Answer 5

Where you choose to define zero elevation

Question 6

What is the equation for the time for a draining reservoir?

Answer 6

t_d = S/A*√2𝑑_0/g

Question 7

What is venturi tube?

Answer 7

A device for determining the volume flux 𝑄 (or equivalently
𝑈) in a pipe

Question 8

Describe characteristic of a venturi tube.

Answer 8

• Narrows in cross section
• Can measure the pressure difference
• Have walls that gently converge or diverge to minimise loss

Question 9

What is the relationship between pressure difference and water level in manometer given by?

Answer 9

P1-P2 = pg∆h