Newton’s Law of Universal Gravitation (Edexcel International A Level Physics)

Newton's Law of Universal Gravitation

• The gravitational force between two masses, e.g., between the Earth and the Sun, is defined by Newton’s Law of Universal Gravitation

• Newton’s Law of Universal Gravitation states:

  The gravitational force F_G between two masses m₁ and m₂ is proportional to the product of their masses and inversely proportional to the square of their separation, r

• In equation form, this is written as:

• Where:

  • F_G = gravitational force between two masses (N)

  • G = Newton’s gravitational constant

  • m₁ and m₂ = mass of body 1 and mass of body 2 (kg)

  • r = distance between the centre of the two masses (m)

• The 1/r² relation is called the ‘inverse square law’

  • This means that if the distance between two masses doubles, r becomes 2r

  • Therefore, 1/r² becomes 1/(2r)², which is equal to 1/4r²

  • Hence, the gravitational force between the two masses reduces by a factor of four

The gravitational force between two masses is defined by Newton’s Law of Universal Gravitation