ASTR 1010 1st Edition Lecture 8Outline of Last Lecture I. Newton’s Laws of MotionA. Definitions Describing MotionOutline of Current LectureI. GravityA. Acceleration of GravityB. Momentum & ForceC. Mass & WeightII. Astronomy FormulasA. DefinitionsB. FormulasCurrent LectureI. Gravity1. Gravity: the force that attracts a body toward the center of the earth, or toward any other physical body having mass. There is gravity in space, but weightlessness is caused by a constant state of freefall. A. Acceleration of Gravity- All falling objects accelerate at the same rate (not counting friction or air resistance).- On Earth, g= 9.8ms2. Speed increases with each second of falling.- Galileo showed that g is the same for all falling objects, regardless of theirmass.B. Momentum & Force- Momentum = mass x velocity- A net force changes momentum, which generally means an acceleration- Rotational momentum of a spinning or orbiting object is known as angular momentum. Angular Momentum = mass x velocity x radius.C. Mass & Weight- Mass: the amount of matter in an object.- Weight: the force that acts upon an object.II. Astronomy FormulasA. Definitions1. Sidereal Time: the hour angle of the vernal equinox at that locality: it has the same value as the right ascension of any celestial body that is crossing the local meridian at that same moment2. Hour angle: the angle between the celestial meridian of an observer and the hour circle of a celestial object measured westward from the meridian.3. Right ascension (RA) and declination (DEC) define the position of a celestial object.B. Formulas- To find Hour Angle (HA): 360˚ = 24 hours 15˚ = 1 hour 1˚ = 4 minutes- To find of the sun/moon is in the east or west.0 h ≤ HA ≤ 6h, it is in the West.18h ≤HA ≤24h, it is in the East.- To find Sidereal Time (ST)ST = RA + HA- To find if a star is circumpolar90˚ - Latitude = Dec circumpolar (n)Every star from n to 90 is circumpolar. Any star –n and below will not be
View Full Document
Unlocking...