gravity

Question 1

Newton’s law of gravitation and formula

Answer 1

any two masses will aattract ech other, gravity never repels

force is proportional to the product of the two masses and proportional to 1/(distance^2)
F = (m1 * m2)

inverse-square law, over distance squared between CENTER OF MASS of each object

put it all together:

F = G * ((m1*m2)/r^2)

BIG G = universal constant, NOT 9.8

Question 2

big G

Answer 2

6.67 x 10^-11 N*m^2/kg^2 ( a very small number, the only reason gravity dominates on larger scales is because electrically neutral)

Question 3

what is r?

Answer 3

the radius/distance of the CENTER OF MASS between mass 1 and mass 2

Question 4

true/false: the force of gravity is MUCH stronger than the electric force on a scale of photons and subatomic particles

Answer 4

FALSE, other way around

Question 5

when do you use f = mg?

Answer 5

at sea level on earth

Question 6

how much would a 500 N person weigh on a plant w/ same average density as earth but double radius?

Answer 6

g = GM/r^2 = G((m/v)(4/3)*pi * r^3)/r^2

= G * (m/v) * 4/3*pi * r

double the force!

Question 7

volume of a sphere?

Answer 7

4/3pir^3

Question 8

what is density?

Answer 8

“rho” (weird p thing)
p = m/v

Question 9

keplers law equations:

Answer 9

T^2 = (r^34pi^2)/GM

v^2 = GM/r

Question 10

keplers laws:

Answer 10

1. planets move in ellipses
2. Planets travel the same “area” in equal time
   3.a planet’s orbital period is proportional to its orbit size

Question 11

does orbit depend on satelite mass (for our purposes in AP Physics 1)?

Answer 11

no