Mass And WeightCopy

Cheat Sheet: Mass, Weight & Gravitational Field (O Level / IGCSE Physics)

1. Mass

• Mass is a measure of the amount of matter in an object.
• It is constant everywhere in the universe.
• SI unit: kilogram (kg)
• Measured at rest relative to the observer

2. Inertia

• Inertia is the tendency of an object to resist any change in its state of motion or rest.
• An object with greater mass has greater inertia (harder to start/stop or change direction).

3. Comparing Masses

• Beam Balance / Equal-Arm Balance:
  • Works on principle of comparing moments
  • Equal masses cause the beam to balance horizontally
  • Works independently of gravitational field strength

4. Measuring Mass: Electronic Balance

• Place object on digital/electronic balance
• Reading displayed directly in grams or kilograms
• Should be zeroed before use for accuracy
• Avoid vibration or air movement during measurement

5. Measuring Weight: Force Meter

• Weight is the gravitational force acting on a mass
• Measured using a spring balance / force meter
• Reading is in Newtons (N)
• Ensure the object is hung vertically and the meter is zeroed first

6. Gravitational Field Strength

• Definition:
  Gravitational field strength is the force per unit mass acting on an object in a gravitational field.
• Equation:
  g = W / m
  where:
  g = gravitational field strength (N/kg)
  W = weight (N)
  m = mass (kg)
• On Earth:
  g ≈ 9.8 N/kg
  (Same as acceleration due to gravity)

7. Gravitational Field

• A gravitational field is a region of space where a mass experiences a gravitational force.
• It is created by any object with mass.
• Always acts towards the centre of the mass causing the field.
• Example: Earth’s gravitational field pulls all objects toward its centre.