Pressure

Question 1

Give the formula for pressure

Answer 1

P = F/A

P. = pressure in Pascals

F = force in Newtons

A = Area in m^2

Question 2

Def a Pascal

Answer 2

It is the unit of Pressure and is equivalent to 1 Newton per sq m

Nm^-2

Question 3

Def Pressure

Answer 3

Is the ratio of force to area

Question 4

Describe how a mercury barometer is made in the laboratory

Answer 4

Inverted glass tube - Sealed at one end
Filled with dry mercury,

Standing vertically in a reservoir of mercury, which is open to the atmosphere

A vacuum exist above column of mercury

Measure the distance above the reservoir mercury to the meniscus in the top of the tube

Standard atmospheric pressure is 760mm
Equivalent to 101 kPa

Question 5

What is used to measure pressure in a fluid

Answer 5

The manometer

Question 6

What exactly is measured with a manometer

Answer 6

The difference between atmospheric pressure and the pressure inside the fluid

Question 7

How is the manometer constructed

Answer 7

A u bent glass tube is filled with mercury

This is connected with an apparatus - the pressure of which is measured

Measure the difference in hight between the two legs of the u tube to get the mercury pressure in mm

Question 8

Why is mercury used in the manometer or barometer?

Answer 8

It has a high density

It makes the column to be measured shorter

(Water would need a column of 10,3m!)

Question 9

Pressure in liquids is measured using the following formula

Answer 9

P = pgh. (roe. gravitational force. Hight)

P = Pa. Pascal
p = (roe). Density in kg.m^-3
g = gravitational force - in m/s2
h = hight ( debth under liquid)

Question 10

What does the gradient on a pressure depth graph represent

Answer 10

Density

Question 11

What formula do we use for calculating hydraulic lifts

Answer 11

F1/A1 = F2/A2