Pressure In Fluids

Question 1

What are fluids?

Answer 1

Substances that can flow (liquids or gases)

Question 2

Pressure in a fluid…

Answer 2

Always produces a force which acts at right angles to the surface of the walls of its container

Question 3

Pressure equations

Answer 3

Pressure (Pa) = force (N) / area (m^2)
Pressure due to liquid above (Pa) = height (m) x density (kg/m^3) x 10N/kg

Question 4

Upthrust =

Answer 4

The weight of fluid displaced

Question 5

If the upthrust is greater than the weight…

Answer 5

The object will accelerate upwards

Question 6

When will an object float?

Answer 6

If the density of the submerged object is less than the density of the water around it then the upthrust force will be greater than the weight of the object and therefore it will float

Question 7

When will an object sink?

Answer 7

If the density of the submerged object is more than the density of the water around it then the upthrust force will be less than the weight of the object and therefore it will sink

Question 8

When will an object have neutral buoyancy?

Answer 8

If the density of the submerged object is equal to the the density of the water around it

Question 9

Why does atmospheric pressure decrease with height?

Answer 9

Due to gravity, air particles in the atmosphere experience a force towards the centre of the earth. The pressure at a given height is caused by the weight of the particles above. As height increases, there are less particles above pushing down on the particles below and therefore pressure decreases with height

Question 10

When a gas particle bumps into the wall of the container…

Answer 10

The wall exerts an equal and opposite force on the particle, causing it to bounce back off the wall

Question 11

In a fixed mass of gas ‘pressure x volume = constant’ but we could also say…

Answer 11

P1 x V1 = P2 x V2 (volume and pressure are inversely proportional)

Question 12

What will happen if work is done on a gas?

Answer 12

It’s internal energy/ KE increases as particles bash into the walls of the container more frequently with a greater force, causing its temperature to rise and its pressure to rise (eg. Bike pumps)

Question 13

Absolute zero

Answer 13

The temperature at which the particles will have completely stopped moving (0K = -237°c). Average KE of particles in a gas is directly proportional to its temperature in kelvins

Question 14

How to change between kelvin and °c

Answer 14

Temperature (K) = temperature (°c) - 273
Temperature (°c) = temperature (K) + 273