Mass & Weight | Physics for GCSE/IGCSE - Year 11 PDF Download

Mass

• Mass represents the amount of matter an object possesses when observed while at rest.
  • Mass is a scalar quantity.
  • The kilogram (kg) is the standard International System of Units (SI) unit for mass.
• Mass is the property of an object that opposes alterations in its motion.
  • Objects with greater mass exhibit increased resistance to changes in speed, deceleration, or alteration of trajectory.
• Mass might occasionally be expressed in grams (g).
  • The conversion between grams and kilograms is: 1000 g equals 1 kg, and 1 g equals 0.001 kg.
• For Example:
  • To convert from kilograms to grams, you multiply by 1000.
  • If an object has a mass of 2.7 kg, it is equivalent to 2700 grams (g).

Weight

• Weight is the gravitational force exerted on an object with mass.
  • Weight, being a force, is classified as a vector quantity.
  • The standard units for force are newtons (N).
• Weight is the consequence of gravitational interaction with mass.
  • Weight is described as the force applied to an object due to gravitational attraction.
• Planets possess potent gravitational fields, leading them to exert a strong gravitational force on nearby masses.
• Weight is accountable for various effects:
  • Objects remain firmly grounded.
  • Objects unfailingly descend towards the ground.
  • Satellites are maintained in orbit.

• The weight of an object equals the result of multiplying its mass (m) by the acceleration due to gravity (g).
  
• This equation can be rearranged using a formula triangle.
  

Gravitational Field Strength

• Gravitational field strength is the force per unit mass acting on an object in a gravitational field.
• On Earth, this value is 9.8 N/kg.
• It is also known as acceleration of free fall, with units in m/s².
• The gravitational field strength g differs from one planet to another based on their mass and radius.
• Below are some examples illustrating the variability of gravitational field strength:

Mass v Weight

• The mass of an object remains constant, but its weight varies according to the gravitational field strength on different planets.
• For instance, on the Moon, where the gravitational field strength is 1.63 N/kg, an object's weight will be approximately six times less than on Earth.
  

Edurev Tip: You're not required to memorize the precise value of g (9.81 N/kg), but you should remember that g is approximately 9.8 N/kg and utilize it in calculations.

Using a Balance

• A balance can be utilized to compare the weight of two objects.
• Due to the consistent gravitational field strength across Earth, this enables the measurement of an object's mass.