Search results
Results From The WOW.Com Content Network
Further, the current usage of "Kepler's Second Law" is something of a misnomer. Kepler had two versions, related in a qualitative sense: the "distance law" and the "area law". The "area law" is what became the Second Law in the set of three; but Kepler did himself not privilege it in that way. [11]
Kepler's laws apply only in the limited case of the two-body problem. Voltaire and Émilie du Châtelet were the first to call them "Kepler's laws". Nearly a century later, Isaac Newton had formulated his three laws of motion. In particular, Newton's second law states that a force F applied to a mass m produces an acceleration a given by the ...
Dividing both force equations by the respective masses, subtracting the second equation from the first, and rearranging gives the equation ¨ = ¨ ¨ = = (+) where we have again used Newton's third law F 12 = −F 21 and where r is the displacement vector from mass 2 to mass 1, as defined above.
Next Newton proves his "Theorema II" which shows that if Kepler's second law results, then the force involved must be along the line between the two bodies. In other words, Newton proves what today might be called the "inverse Kepler problem": the orbit characteristics require the force to depend on the inverse square of the distance. [3]: 107
This is Kepler's second law of planetary motion. The square of this quotient is proportional to the parameter (that is, the latus rectum) of the orbit and the sum of the mass of the Sun and the body. This is a modified form of Kepler's third law. He next defines: 2p as the parameter (i.e., the latus rectum) of a body's orbit,
Thus, the areal velocity is constant for a particle acted upon by any type of central force; this is Kepler's second law. [13] Conversely, if the motion under a conservative force F is planar and has constant areal velocity for all initial conditions of the radius r and velocity v, then the azimuthal acceleration a φ is always zero.
Illustration of Kepler's second law. The planet moves faster near the Sun, so the same area is swept out in a given time as at larger distances, where the planet moves more slowly. Areal velocity is closely related to angular momentum. Any object has an orbital angular momentum about an origin, and this turns out to be, up to a multiplicative ...
Kepler's third is a direct consequence of the second law. Integrating over one revolution gives the orbital period [ 1 ] T = 2 π a b h {\displaystyle T={\frac {2\pi ab}{h}}} for the area π a b {\displaystyle \pi ab} of an ellipse.