Gravitation Flashcards
Newton’s law of _______ describes ________ ________ between any two objects.
gravitation
gravitational attraction
Every particle attracts every other particle with a force ________ proportional to the ________ of the masses of the particles and _________ proportional to the _________ of the distance between them.
directly
product
inversely
square
Any two particles attract each other through __________ forces which are ________ in magnitude even if particles have ________ masses.
gravitational
equal
different
If distance between two particles is doubled, the gravitational force between them is _________ as great.
1/4
The equation for weight is _________.
w = m*g
For any objects that have spherically symmetrical mass distributions, they can be modelled as if ____________________.
mass was concentrated at center.
As object is moved towards the center of the earth the gravitational force __________. At exactly the center of the earth the force on the object is _________.
decreases
zero
Gravitational forces from all directions cause objects to take a ___________ shape. For ________ objects the force is greater and the more spherical they are. For _______ objects the force is smaller and they retain an irregular shape.
spherical
heavier
lighter
Use __________ to determine gravitational constant G.
Cavendish torsion balance
Gravitational forces combine ________. If each of 2 masses exerts a force on a third, total force on the third is the ________ of the individual forces of the first two.
vectorially
vector sum
_________ also applies to gravitation forces. Bc even if objects have different masses and feel the same magnitude of force from the other, the response to the force is ________ for each object.
Newton’s third law
different
________ holds earth together and keeps planets in orbit around the sun.
gravity
______________ between different parts of the sun compresses material at its core to very high densities and temperatures so nuclear reactions are able to take place.
mutual gravitational attraction
The formula for acceleration is ____________.
a = Fg/m
______ of an object is the total gravitational force exerted on the object by all other objects in the universe.
weight
the equation for weight is ________ or _______.
w = Fg = (GmEm)/RE^2
w = m*g
The equation for acceleration due to gravity is __________. It is ____________ of mass.
g = (G*mE)/RE^2
independent
The equation for weight of an object at a distance from center of the earth is given by _________.
w = Fg = (GmEm)/r^2
Weight of an object _______ inversely with the square of its distance from the earths center.
decreases
The apparent weight of an object _______ _______ from gravitational force because earth rotates and is not precisely an inertial frame of reference.
differs slighly
The equation for volume of a sphere is __________.
VE = 4/3 * pi * RE^3
Gravitational potential energy is proportional to _______ while potential energy is proportional to ________.
1/r^2
1/r
When object moves away from earth, r increases, gravitational force does _________ work and U _________. When an object falls toward earth, r decreases, gravitational work is _________ and U ________.
negative
increases
positive
decreases
U is zero when object of mass m is ___________ the earth.
infinitely far from
Total mechanical energy of the system of earth and object is ________/_________.
constant
conserved
______ orbits will return to origin at same speed and repeat motion indefinitely. ______ orbits never return to starting point but travel every farther from the earth.
closed
open
The only force acting on a satellite in circular orbit around the earth is _____________ directed toward the center of the earth and toward center of the orbit. It has _______ circular motion.
earths gravitational attraction
uniform
In a circular orbit the speed is just right to keep the distance from the satellite to the center of the earth ________.
constant
Relationship between orbit radius and speed mean _______ choose them independently.
cannot
Motion of a satellite ________ on mass.
does not depend
Apparent weightlessness occurs when _______________.
gravity is the only force acting on a spacecraft.
True weightlessness occurs if an astronaut is __________ from any other masses and gravitational force is _________.
infinitely far
zero
Larger orbits correspond to __________ speeds and ________ periods.
slower
longer
Escape speed from a spherical object with radius R is __________ than speed of a satellite in a circular orbit at that radius.
sqrt 2 times greater
Total mechanical energy in a circular orbit is ________ and equal to ________ the potential energy. Increasing orbit radius means _________ total mechanical energy.
negative
0.5
increasing
The larger the radius of a satellites orbit, the ________ the total mechanical energy, the _________ the potential energy, and the _________ the kinetic energy.
greater
greater
smaller
Kepler’s first law states that each planet moves in _________ orbit, with the sun at one focus of the ________.
elliptical
ellipse
Kepler’s 2nd law states: a line from the sun to a given planet sweeps out ________ areas in _______ times.
equal
equal
Kepler’s 3rd law states: the periods of the planets are proportional to the _________ powers of the major axis lengths of their orbits.
3/2
________ is a measure on how intense the ellipse is. At e=_____ the ellipse is a circle.
eccentricity
0
The point in the planet’s orbit closest to the sun is the _________ and the point most distant is the __________.
perihelion
aphelion
Closed orbits have shape ______ or ______. Open orbits have shape _______ or _______.
circle
ellipse
parabolas
hyperbolas
From kepler’s 2nd law: sector velocity has _________ at all points in the orbit. When planet is close to the sun, r is ______ and dtheta/dt is _______. When planet is far from sun, r is _______ and dtheta/dt is ________.
same value
small
large
large
small
Period _______ depend on eccentricity.
does not
Sun ______ stationary because of ___________.
is not
gravitational force of same magnitude but opposite direction
_______ of a star can help discover other plants in orbit around other stars.
wobble
__________ is the idea that objects in celestial realms obey the same laws of motion as objects on earth.
newtonian synthesis
Earth is not precisely an inertial frame of reference because it ___________.
rotates on its axis
Apparent weight of an object on earth is ____________ to the earth gravitational attraction.
not precisely equal
The earths gravitational attraction is the __________ of an object.
true weight
Apparent weight is the same as true weight at _________ or __________.
north pole
south pole
Except a poles, the apparent weight is _______ than the gravitational force of attraction on the object.
less
Because earth is rotating, a falling object at equator has acceleration _________. If earth was not rotating the object would have free fall acceleration __________.
g0 = w0/m
g = w/m
If a spherical nonrotating object with mass M hs radius ______ Rs, then nothing can escape the surface of the black hole.
<=
The surface of the sphere with radius Rs surrounding a black hole is the __________ as we cannot __________.
event horizon
observe events occurring inside
From outside the even horizon all an observer can know about a black hole is ________, __________ and ________.
mass, electric charge, angular momentum.
Closer to a black hole clocks run ______, an effect called _______.
slower
time dilation
___________ theorized that planets orbit around the sun (_________ model) in circular orbits.
Copernicus
heliocentric
The __________ is a circular orbit that itself moves in along a much larger circular orbit. This is a ________ orbit.
epicycles
copernicus
The _________ orbit is a circular orbit that itself moves in an _________ orbit.
