Lecture 3-4

Question 1

Pressure from a molecular view is stated as

Answer 1

momentum change of molecule during impacts causes vertical or normal reaction force on surface

Question 2

Pressure =

Answer 2

normal force due to all impacts on the unit area

F/A

Question 3

Vacuum pressure is calculated by

Answer 3

P atmospheric - P absolute

Question 4

Gauge pressure is calculated by

Answer 4

P absolute - P atmospheric

Question 5

Pressure is equal in all

Answer 5

directions

Question 6

d P / d z =

Answer 6

change in pressure / change in the z-axis =

• ρ g
• density x gravity

Question 7

Pressure is ———- —- ——— ——– if points are interconnected by the same fluid

Answer 7

constant on horizontal planes

Question 8

P1 = P2

so F2 / F1 =

Answer 8

P2 A2 / P1 A1 = A2 / A1

Question 9

The ratio of areas on each side of a hydraulic lift are called

Answer 9

ideal mechanical advantage

Question 10

Pascal’s Law states that

Answer 10

the pressure applied to a confined fluid increases the pressure throughout by the same amount

Question 11

Why are pressure changes in gases only felt when a large variation in the z-axis (height) is experienced?

Answer 11

As ρ is small in gases, the dP / dz = -ρg the dz must be large for there to be a significant dP change

Question 12

Mercury Barometer: how does it read?

Answer 12

height of mercury in the closed glass tube indicates pressure

Question 13

Piezometer tube: how does it read?

Answer 13

height of fluid in the open standpipe indicates pressure

Question 14

Mercury Barometer: what pressure does it indicate?

Answer 14

absolute pressure

Question 15

Piezometer tube: what pressure does it indicate?

Answer 15

gauge pressure

Question 16

U-tube manometer: what pressure does it indicate?

Answer 16

gauge pressure

Question 17

U-tube manometer: what does it read?

Answer 17

height of fluid in open U-tube

Question 18

Piezometer tubes can be used for measuring the pressure of

Answer 18

ONLY liquids

Question 19

U-tube manometer can be used to measure the pressure of

Answer 19

liquids and gases

Question 20

When would you use a differential U-tube manometer or an inclined differential U-tube manometer?

Answer 20

When measuring a pressure difference between two reservoirs

Question 21

An inclined differential U-tube manometer is used when

Answer 21

measuring a small pressure difference in two reservoirs

Question 22

Bourdon pressure gauges indicate a pressure reading by ….. then …..

Answer 22

deformation of an elastic element which is mechanically linked to a needle indicator

Question 23

Strain-gauge diaphragm pressure transducers use the deformation of a —- to represent pressure

Answer 23

diaphragm

Question 24

A deadweight tester uses a —– in a chamber applying a force on —– which is then transferred to a —– —— —-

Answer 24

piston, oil, reference pressure port