Basic Speed, Density & Pressure

 
What Are Speed, Density, and Pressure?

Speed, density, and pressure are commonly used compound measures. They describe relationships between different physical quantities.

Key Formulas:

Speed = $\frac{ \text{Distance} }{ \text{Time} }$

Density = $\frac{ \text{Mass} }{ \text{Volume} }$

Pressure =  $\frac{ \text{Force} }{ \text{Area} }$

Each of these equations represents how one quantity changes in proportion to another.

Formula Triangle Method

To make rearranging formulas easier, use formula triangles:

To find a missing value, cover it up in the triangle and use the remaining formula.

 
Speed, Distance, and Time

Speed is a measure of how fast something is moving and is commonly measured in:

• Metres per second (m/s)
• Kilometres per hour (km/h)

Formula:

$$\text{Speed} = \frac{ \text{Distance} }{ \text{Time} }$$

Example:

A car travels 240 km in 4 hours. Find its speed.

Step 1: Use the formula

$$\text{Speed} = \frac{240}{4} = 60 \text{km/h}$$

Final Answer: The car is travelling at 60 km/h.

 
Density, Mass, and Volume

Density measures how much mass is packed into a certain volume. It is commonly measured in:

Grams per cubic centimetre $(\text{g/cm}^3)$

Kilograms per cubic metre  $(\text{kg/m}^3)$

Formula:

$$\text{Density} = \frac{ \text{Mass} }{ \text{Volume} }$$

Example:

A metal block has a mass of 300 g and a volume of $60 \text{cm}^3$. Find its density.

Step 1: Use the formula

$$\text{Density} = \frac{ 300 }{ 60 } = 5 \text{g/cm}^3$$

Final Answer: The density of the metal is $5 \text{g/cm}^3$.

 
Pressure, Force, and Area

Pressure measures how much force is applied over a certain area. It is commonly measured in:

Newtons per square metre (N/m²), also known as Pascals (Pa).

Formula:

$$\text{Pressure} = \frac{ \text{Force} }{ \text{Area} }$$

Example:

A box exerts a force of 120 N over an area of 30 $m^2$. Find the pressure.

Step 1: Use the formula

$$\text{Pressure} = \frac{ 120 }{ 30 } = 4 \text{N/m}^2$$

 
Final Answer: The pressure is 4 $\text{N/m}^2$ (or 4 Pa).