L5 physics and gravity

speed

rate at which object moves, distance/time in m/s

velocity

speed AND direction e.g. 10 m/s due east

Galileo showed that g is

same for all falling objects regardless of mass

momentum changed by

a net force, usually meaning an acceleration

angular momentum

rotational momentum of a spinning or orbiting object

what is needed to change an object’s angular momentum

a torque

mass

a measure of amount of matter in an object

weight

the force that a scale exerts upon an object

why are astronauts weightless in space

there is gravity and in a continued state of free fall

what did newton do

extrapolated physical laws of Earth to heavens, laws of motion and gravity, experiments with light, invention of calculus

newton’s first law of motion

an object moves at constant velocity unless a net force acts to change its speed or direction

newton’s second law of motion

force = mass x acceleration = rate of change in momentum

newton’s third law of motion

for every force there is always an equal and opposite reaction force

conservation of momentum

objects continue at constant velocity, total momentum of interacting objects cannot change unless an external force is acting on them + they exchange momentum through equal and opposite forces

conservation of angular momentum

figure skater bringing arms in makes them go faster

types of energy

kinetic = motion, radiative = light, potential = stored

conservation of energy

energy can transfer between objects or change forms, but cannot be created or destroyed

thermal energy

the collective KE of many particles, depending on both temperature and density

temperature

measure of the average KE of many particles in a substance

on Earth, gravitational potential energy depends on 

object’s mass, strength of gravity, and height above the ground

object/gas cloud and gravitational potential energy

has more when it is spread out than when it contracts, which converts it to thermal energy

mass energy relationship

E = mc² - small mass, big energy

concentrated energy can spontaneously 

turn into particles

universal law of gravitation

every mass attracts every other mass with F_g = Gm₁m₂/d²

G is gravitational constant, d is distance between them

types of orbital paths

bound (ellipses) and unbound (parabola, hyperbola) e..g extra-solarsystem comet that just leaves

center of mass and orbits

because of angular momentum conservation, orbiting objects orbit around their combined center of mass

gain or loss of orbital energy from

gravitational encounter, friction or atmospheric drag

escape velocity

if an object gains enough orbital energy, it may escape (change from bound to unbound orbit

angular momentum equation

mass x velocity x radius

total mass of a system from orbits/ newton and kepler’s third law

M₁ + M₂ = 4π²a³/Gp² (p = orbital period, a = avg orbital distance between centers)

total orbital energy is

constant ; gravitational potential + kinetic energies

causation of tides

Moon’s gravity pulls harder on near side of Earth than on far side

tidal friction

gradually slows Earth’s rotation and makes Moon get farther, caused Moon’s tidal locking - removal of energy from the system

spring tide

new moon and full moon, tidal forces of Sun and Moon work together to create lowest lows and highest highs

neap tide

first and third quarters, Sun and Moon work against each other, highest lows and lowest highs

relationship between gravitational acceleration and mass

DOES NOT EXIST