Week 2 Gravity, Earth, Moon, Parallax, Brightness Distances & Magnitudes Flashcards
what is the gravitational force equation
F = -GMm / r^2
what is always true of the gravitational force and why
it is always attractive since you can only have positive mass
what is the acceleration due to gravity equation
g = GM / r^2
what is the gravitational energy equation
E = -GMm / r
what is the escape velocity equation
vesc = sqrt[ 2GM / r ]
what is the orbital velocity equation
vorb = sqrt[ GM / r ]
what two factors can be used to find the circumference of the orbit of an object around another
time period of the orbit
velocity of the object orbiting
what is the general simple procedure for determining the distance of an object very far away
look at an object and measure the angle between you and it
step sideways and re measure this angle
now calculate the change in angle and the distance of the sideways step
input into this equation
d = b / tanθ
b is the sidestep distance
what do astronomers use as an appropriate sidestep
the orbit of the Earth
what is the distance equation in parsec
d = 1 / p
p is the parallax angle in arcseconds
define proper motion
star positions change in the sky position because of parallax and their relative velocities
what is the proper motion equation
μ = v / d
μ is in radian per second
give the four useful circle and sphere equations
c = 2πr A = πr^2 A = 4πr^2 V = 4/3 πr^3
when is parallax not useful
measuring distance of objects outside our galaxy
what method do we use to measure distance to objects outside our galaxy
brightness distances
