5.1.4 Weight, Mass & Gravity

• What is the definition of mass?

  Mass is the amount of matter in an object.
• What type of quantity is mass?

  Mass is a scalar quantity, meaning it only has magnitude.
• In what unit is mass measured?

  Mass is measured in kilograms (kg).
• How does mass change with location?

  Mass does not change regardless of the location of the object.
• What is the definition of weight?

  Weight is the force exerted on an object due to gravity.
• What type of quantity is weight?

  Weight is a vector quantity, meaning it has both magnitude and direction.
• How can weight be calculated?

  Weight can be calculated using the formula: Weight (W) = Mass (m) × Gravitational Field Strength (g).
• In what unit is weight measured?

  Weight is measured in Newtons (N).
• What is the approximate value of gravitational field strength (g) on Earth?

  On Earth, g ≈ 9.8 N/kg.
• How does gravitational field strength vary?

  The value of g varies depending on where you are.
• What is the approximate value of gravitational field strength (g) on the Moon?

  On the Moon, g ≈ 1.6 N/kg.
• How does weight change with location?

  Unlike mass, weight can change depending on the location because it depends on the gravitational field strength.
• What is the definition of gravity?

  Gravity is the force of attraction between two masses.
• What does gravity do to objects?

  Gravity pulls objects towards the center of the mass of a planet, star, or moon.
• What is the Universal Law of Gravitation?

  Every mass attracts every other mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
• What does the formula F = G(m1 × m2) / r² represent?

  This formula represents the force of gravity between two masses.
• What do m1 and m2 represent in the Universal Law of Gravitation formula?

  m1 and m2 represent the two masses involved in the gravitational attraction.
• What does r represent in the Universal Law of Gravitation formula?


  r represents the distance between the centers of the two masses.
• What is gravitational field strength?


  Gravitational field strength is a measure of the force of gravity at a particular location.
• What is the relationship between mass, weight, and gravity?

  • Mass is an intrinsic property of an object and does not change based on location.
  • Weight is the force experienced by a mass due to gravity.
  • On Earth: W = m × 9.8 N/kg
  • On the Moon: W = m × 1.6 N/kg
  • Gravity is the force that causes the object to have weight.
• How do you calculate weight on Earth and the Moon?

  1. Weight on Earth: W = m × 9.8 N/kg

  2. Weight on the Moon: W = m × 1.6 N/kg

  3. Example: For a mass of 50 kg:

  • On Earth: W = 50 kg × 9.8 N/kg = 490 N
  • On the Moon: W = 50 kg × 1.6 N/kg = 80 N
• What are the practical implications of understanding mass, weight, and gravity?

  • Astronomy: Essential for space exploration and calculating forces for spacecraft.
  • Engineering: Important for designing structures and vehicles under different gravitational conditions.
  • Health: Astronauts must adapt to different weights in space, although their mass remains unchanged.
• What are the key points about mass, weight, and gravity?

  • Mass is constant and measured in kilograms (kg).
  • Weight is a force due to gravity, measured in Newtons (N), and varies with gravitational field strength.
  • Gravity is the force that attracts objects towards the center of a planet, star, or other large body.