Hydraulics

Question 1

For practical purposes how many litres does 1 litre of water weigh in newtons?

Answer 1

10 newtons

Question 2

For practical purposes how much does 1 cubic meter of water weigh in newtons?

Answer 2

10,000 Newtons

Question 3

Give 4 properties of water

Answer 3

Virtually incompressible
Incapable of resisting change of shape
Good conductor of electricity
Freezing point 0°C and boiling point 100°C when at normal atmospheric pressure

Question 4

What is normal atmospheric pressure?

Answer 4

1.013 bar

Question 5

What is the formula used to calculate water power?

Answer 5

WP = 100 x L x P ÷ 60

Where L is the flowrate in litres per minute
P is the increase in pressure between the inlet and outlet measured in bar
WP is water power measured in watts

Question 6

Define jet reaction

Answer 6

The reaction equal and opposite to the force required to discharge the jet at the nozzle resulting in a recoil in the opposite direction to the flow

Question 7

What factors affect the loss of pressure due to friction

Answer 7

Length of hose
Roughness of the inside surface of the hose
Flow rate of the liquid in the hose
Hose/pipe diameter

Question 8

Define atmospheric pressure

Answer 8

Is the force per unit area exerted on a surface by the weight of air above

Question 9

What are the 5 principle characteristics of pressure?

Answer 9

1) Pressure exerted by a fluid at rest is always at right angles to the surface of the vessel which contains it
2) the pressure at any point in a fluid at rest is the same in all directions
3) downward pressure of a fluid in an open vessel is proportional to its depth
4) downward pressure of a fluid in an open vessel is proportional to the density of the fluid
5) downward pressure of a fluid on the bottom of a vessel is independent of the shape of that vessel

Question 10

As water flows through a channel what forms of energy may be present?

Answer 10

Kinetic - (because of the velocity)
Potential (because of its height above a fixed reference point)
Pressure
Heat

Question 11

What does CREST stand for?

Answer 11

Create flow
Resistance to flow
Entry loss
Strainers
Temperature

Question 12

What is the greatest depth a pump can lift water from?

Answer 12

10.3m theoretically
8m practically - as the pump has to overcome CREST which reduces the pump output