Kinetics

Newton's law of universal gravitation will help us understand gravitational force. Bodies attract other bodies with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Mathematically the equation of gravitational force states the following:

where F_g is gravitational force, G⁴² is the universal gravitational constant (G = 6,67.10^–11 N⋅m²⋅kg^–2), m₁ and m₂, are masses of two bodies, and r is the distance between the masses.

Gravitational forces between bodies are insignificant in sport activities and we can neglect their existence. Only one body has a significant effect on other bodies in sporting activities (and everyday life) – planet Earth. The Earth has such an enormous mass that its gravitational force has an effect on all moving bodies. Weight of bodies and gravitational force are thus caused mostly by the Earth’s gravity. Gravitational force is not the only force exerted by the Earth – there is also (much smaller) centrifugal force caused by the Earth’s rotation about its axe⁴³. The resultant force, composed of gravitational and centrifugal forces, is called local gravity (or sometimes effective gravity) F_G.

⁴² Universal gravitational constant is also sometimes denoted by the Greek letter kappa – κ.Zpět

⁴³ The influence of centrifugal force in sporting activities is usually negligible.Zpět