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Newton's laws are often stated in terms of point or particle masses, that is, bodies whose volume is negligible. This is a reasonable approximation for real bodies when the motion of internal parts can be neglected, and when the separation between bodies is much larger than the size of each.
The laws of physics are the same for all observers in any inertial frame of reference relative to one another (principle of relativity). The speed of light in vacuum is the same for all observers, regardless of their relative motion or of the motion of the light source. The resultant theory copes with experiment better than classical mechanics.
Before Newton's law of gravity, there were many theories explaining gravity. Philoshophers made observations about things falling down − and developed theories why they do – as early as Aristotle who thought that rocks fall to the ground because seeking the ground was an essential part of their nature.
There are two main descriptions of motion: dynamics and kinematics.Dynamics is general, since the momenta, forces and energy of the particles are taken into account. In this instance, sometimes the term dynamics refers to the differential equations that the system satisfies (e.g., Newton's second law or Euler–Lagrange equations), and sometimes to the solutions to those equations.
Sir Isaac Newton (/ ˈ nj uː t ən /; 4 January [O.S. 25 December] 1643 – 31 March [O.S. 20 March] 1727) [a] was an English polymath active as a mathematician, physicist, astronomer, alchemist, theologian, and author. [5] Newton was a key figure in the Scientific Revolution and the Enlightenment that followed. [6]
This includes Newton's law of universal gravitation, and the relation between gravitational potential and field acceleration. d 2 R / dt 2 and F / m are both equal to the gravitational acceleration g (equivalent to the inertial acceleration, so same mathematical form, but also defined as gravitational force per unit mass [8 ...
1684 – Isaac Newton proves that planets moving under an inverse-square force law will obey Kepler's laws in a letter to Edmond Halley. [7] 1686 – Isaac Newton uses a fixed length pendulum with weights of varying composition to test the weak equivalence principle to 1 part in 1000. [9] [10]
In 1676–77, Isaac Newton combined Kepler's laws of planetary motion with Huygens' ideas, refined them, and found the proposition that by a centrifugal force reciprocally as the square of the distance a planet must revolve in an ellipsis about the center of the force placed in the lower umbilicus of the ellipsis, and with a radius drawn to ...