Standard Units

Different types of measurements require different kinds of units. Understanding standard units ensures that everyone is on the same page. This is particularly important when measuring various quantities like length, time and volume.

Let’s look at some of these standard units used in different scenarios.

Important Standard Units

Distance

• For long distances, the common units are kilometres (km) and miles.

• For shorter distances, we typically use metres (m), centimetres (cm) and millimetres (mm).

Area and Volume

• Area: It is commonly measured in km², m², cm², and mm².

• Volume: The standard units include m³, cm³, and mm³.

Speed

Speed is often expressed in meters per second (m/s), kilometres per hour (km/h), and miles per hour (mph).

The formula for speed is:

Speed = Distance ÷ Time

Density

Density is calculated as mass divided by volume. The units for density are kg/m^{3} and g/cm^{3}.

The formula for density is:

Density = Mass ÷ Volume

Pressure

Pressure is defined as force divided by area. It is commonly measured in Pascals (Pa).

The formula is:

Pressure = Force ÷ Area

Important Unit Conversions

Knowing how to convert between units is very useful. Here are some important conversions:

Length

• 1 cm = 10 mm

• 1 m = 100 cm

• 1 km = 1000 m

Mass

• 1 g = 1000 mg

• 1 kg = 1000 g

• 1 tonne = 1000 kg

Capacity

• 1 cm³ = 1 ml

• 1 litre = 1000 ml

• 1 litre = 1000 cm³

Practice Questions

Question 1:

Convert 5000 m to km.

Solution

To convert metres to kilometres, divide by 1000.

So, 5000 m = 5 km.

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Question 2:

What is the speed if you travel 120 km in 2 hours?

Solution

Speed = Distance ÷ Time

= 120 km ÷ 2 hours

= 60 km/h

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Question 3:

Calculate the density of an object that has a mass of 300 g and a volume of 100 cm³.

Solution

Density = Mass ÷ Volume

= 300 g ÷ 100 cm³

= 3 g/cm³

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Question 4:

If a force of 200 N is applied over an area of 40 cm², what is the pressure?

Solution

Pressure = Force ÷ Area

= 200 N ÷ 40 cm²

= 5 N/cm²

Convert it to Pascals if needed, remembering that $1 N/cm² = 10,000 Pa, so the pressure is 50,000 Pa.