Gravitation
Physics · गुरुत्वाकर्षण · 15 facts
Newton's Law of Gravitation: F = Gm1m2/r2; every mass attracts every other mass
G (gravitational constant) = 6.674 x 10^-11 Nm2/kg2; universal constant
g (acceleration due to gravity) = 9.8 m/s2 on Earth surface
g is maximum at poles, minimum at equator (Earth shape and rotation)
g decreases with altitude (above surface) and depth (below surface)
Weight = mass x g; weight changes with location but mass remains constant
Weight on Moon = 1/6th of Earth (Moon g = 1.63 m/s2)
Escape velocity of Earth = 11.2 km/s; minimum speed to leave Earth gravity
Orbital velocity for low Earth orbit = 7.9 km/s
Kepler 1st Law: planets orbit in ellipses with Sun at one focus
Kepler 2nd Law: planet-Sun line sweeps equal areas in equal times
Kepler 3rd Law: T2 proportional to r3; farther planet = longer orbital period
Geostationary orbit: satellite appears fixed, period=24hrs, height=36000km
Henry Cavendish measured G using torsion balance experiment (1798)
Weightlessness in satellite: astronaut in continuous free fall, apparent weight=0