Universal Gravitation

Tycho Brache

Teacher of kepler, mapped the night sky over 20 years of observation

epicyle

smaller circular path followed along a larger circular path

johanes kepler

astronomer who used geometry and mathematics with sun-centered solar system to calc the motion of the planets; developed three laws that describe the behaviour of

keplers first law of planetary motion

the paths of the planets are ellipses with the center of the sun at one focus; went against the belief that the planets follow a circular orbit

ellipse

oval shape drawn above two foci; in the equation of an ellipse, “a” is the radius along the x-axis and “b” is the radius along the y-axis

Keplers second law of planetary motion

an imaginary line form the sun to a planet sweeps out equal areas in equal time intervals; planets move fastest when closest to the sun and slowest when farthest from the sun’ went against the belief that the Earth is stationary and proposed the idea that planets travel at varying speeds throughout their orbits.

period

(T) time to complete one full cycle of motion

Keplers third law of planetary motion

the ratio of the squares of the periods of any two planets revolving about the sun is equal to the ratio of the cubes of their average distances from the sun, where T is period, r is average distance from the sun, and “a” and “b” represent two planets; provided accurate date for the distance the planets are from the sun.

inverse square law

variance of physical quantities inversely as another quantity squared

law of universal gravitation

For any pair of objectives, each object attracts the other with a force directly proportional to the product of the masses of the objects, and inversely proportional to the square of the distance between centers

universal gravitational constant

constant used to provide the proper units and proportion when using Newton’s Law of universal Gravitation

Henry Cavendish

measured the value of G

support force

force that completely balances the weight of an object at rest; normal force

apparent weightlessness

experiencing the effects of zero gravity due to the lack of a support force; g = 0

gravity

the way in which masses communicate with one another