4.5.5 Pressure And Pressure Differences In Fluids

Question 1

What is a fluid?

Answer 1

Either a liquid or gas

Question 2

What does the pressure in fluids cause?

Answer 2

A force normal (at right angles) to any surface

Question 3

The equation used to calculate the pressure at the surface of a fluid

Answer 3

Pressure = force normal to a surface /area of that surface [p=F/A]

Question 4

Pressure unit

Answer 4

Pressure, p, in pascals, Pa

Question 5

Force unit

Answer 5

Force, F, in newtons, N

Question 6

Area unit

Answer 6

Area, A, in metres squared, m^2

Question 7

How to calculate pressure due to a column of liquid?

Answer 7

Pressure = height of the column x density of the liquid x gravitational field strength [p= h p g ]

Question 8

Pressure unit

Answer 8

Pressure, p, in pascals, Pa

Question 9

Height unit

Answer 9

Height of the column, h, in metres, m

Question 10

Density unit

Answer 10

Density, p, in kilograms per metres cubed, Kg/m^3

Question 11

Gravitational field strength unit

Answer 11

Gravitational field strength, g, in newtons per kilogram. N/kg

Question 12

Why in a liquid, does the pressure increase with the height of the column of liquid above that point and with the density of the liquid

Answer 12

Pressure increases as the depth increases. The pressure in a liquid is due to the weight of the column of water above. Since the particles in a liquid are tightly packed, this pressure acts in all directions.

Question 13

What is the upthrust force?

Answer 13

A partially (or totally) submerged object experiences a greater pressure on the bottom surface that on the top surface. This creates a resultant force upwards ( called the upthrust)

Question 14

What are the factors which influence floating or sinking?

Answer 14

If an object has a density less than that of water, it will float. If an object has a density more than that of water, it will sink.

Question 15

What is the atmospheres pressure size?

Answer 15

The atmosphere is a thin layer (relative to the size of the Earth) of air around the Earth. The atmosphere gets less dense with increasing altitude

Question 16

What creates atmospheric pressure?

Answer 16

Air molecules colliding with a surface.

Question 17

What happens to the number of air molecules as the height of the surface above ground increases?

Answer 17

The number of air molecules above a surface decreases as the height of the surface above ground level increases. So as height increases there’s always less air above a surface than there is at a lower height. So atmospheric pressure decreases with an increases in height

Question 18

Describe a simple model of the Earth’s atmosphere and of atmospheric pressure?

Answer 18

The earths atmosphere is the layer surrounding the earth and the pressure decreases with altitude because there are less molecules as you go higher

Question 19

Explain why atmospheric pressure varies with height above a surface ?

Answer 19

At higher elevations, there are fewer air molecules above a given surface than a similar surface at lower levels.