Equations of motion system). Particle does not exert a torque on itself. Some examples of Newton's law include describing the motion of a simple pendulum, and a damped, sinusoidally driven harmonic oscillator, For describing the motion of masses due to gravity, Newton's law of gravity can be combined with Newton's second law. For two examples, a ball of mass thrown in the air, in air currents (such as wind) described by a vector field of resistive forces , where is the gravitational constant, the mass of the Earth, and is the acceleration of the projectile due to the air currents at position and
Kepler's laws of planetary motion laws fit the observations better than does the model proposed by Copernicus. Kepler's corrections are not at all obvious: The eccentricity of the orbit of the Earth makes the time from the March equinox to the September equinox, around 186 days, unequal to the time from the September equinox to the March equinox, around 179 days. A diameter would cut the orbit into equal parts, but the plane through the Sun parallel to the equator of the Earth cuts the orbit into two parts with areas in a 186 to 179 ratio, so the eccentricity of the orbit of the