How to Determine the Density of Regular and Irregular Solid Objects

Introduction

• This lecture is focused on understanding how to determine the density of both regular and irregular solid objects.
• This is a required practical and may appear in exams.
• Density: It is the mass of a material per unit volume.
• Density Equation: Density = Mass (kg) / Volume (m³)
  • Units: Kilograms per cubic meter (kg/m³)

Determining Density of Regular Objects

• Regular Objects: Objects with easy-to-measure dimensions (e.g., a cube).
• Steps:
  1. Determine Mass: Use a balance to find the mass.
  2. Measure Dimensions: Use a ruler to measure the length of each side.
     • Example: A cube with side length of 120 mm (0.12 m).
  3. Calculate Volume: Volume = side length³
     • Example Calculation: 0.12 m x 0.12 m x 0.12 m = 0.001728 m³
  4. Calculate Density: Use the density formula.
     • Example: Mass 0.5 kg and volume 0.001728 m³ gives a density of 28935 kg/m³.

Determining Density of Irregular Objects

• Irregular Objects: Objects whose dimensions are not easily measured (e.g., a vase).
• Method Used: Displacement method.
• Steps:
  1. Determine Mass: Use a balance to find the mass.
  2. Use a Eureka Can: Fill it with water; it has a spout for displaced water.
  3. Displacement: Place the object in the water to displace it.
  4. Measure Displaced Water Volume: Use a measuring cylinder to find the volume of displaced water.
     • This volume equals the object's volume.
  5. Calculate Density: Use the density formula with the known mass and displaced volume.

Conclusion

• By understanding these methods, one can effectively determine the density of both regular and irregular objects.
• Practice with questions in the revision workbook for further understanding and preparation.