Newton’s law of gravitation

• Newton’s law of gravitation
• Gravitational field strength

Applications and skills:

• Describing the relationship between gravitational force and centripetal force
• Applying Newton’s law of gravitation to the motion of an object in circular orbit around a point mass
• Solving problems involving gravitational force, gravitational field strength, orbital speed and orbital period
• Determining the resultant gravitational field strength due to two bodies

Guidance:

• Newton’s law of gravitation should be extended to spherical masses of uniform density by assuming that their mass is concentrated at their centre
• Gravitational field strength at a point is the force per unit mass experienced by a small point mass at that point
• Calculations of the resultant gravitational field strength due to two bodies will be restricted to points along the straight line joining the bodies

Data booklet reference:

• The laws of mechanics along with the law of gravitation create the deterministic nature of classical physics. Are classical physics and modern physics compatible? Do other areas of knowledge also have a similar division between classical and modern in their historical development?

Utilization:

• The law of gravitation is essential in describing the motion of satellites, planets, moons and entire galaxies
• Comparison to Coulomb’s law (see Physics sub-topic 5.1)

Aims:

• Aim 4: the theory of gravitation when combined and synthesized with the rest of the laws of mechanics allows detailed predictions about the future position and motion of planets