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### Cambridge AS levels

Computer Science Chemistry Reference Questions

### Programming and coding

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# Pressure, density & mass

Before, you get know what is density and pressure. We need to know what is mass

The formal definition of mass is the amount of inertia or resistant to change in motion. A less informal definition is the amount of matter or substance an object has

## Density

### The mass per unit volume

SI units: kgm-3

#### D = m/v

Sometimes they give density in gcm-3 So remember this:

## Pressure

### It is the force acting on per unit area

SI units: Pascals or Nm-2

Remember that 1 atm = 105Pa

## Pressure in Liquids

Pressure in liquids act in all directions and it increases with depth and doesn't depend on the shape of the container

#### P = dgh

The derivation is sometimes asked in Mcqs

#### P = hdg

So where is pressure examples used in:

• Boyles law - A2
• This is covered in A levels

• Manometer
• So this actually measures the pressure difference. The difference in height tells us the difference in pressure in term of hdg. In other words, the pressure at one end is greater than the other end by hdg