Edexcel A Level Physics:复习笔记12.3 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 FG 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:
  • FG = 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