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PHYS 124 > Gravitation > Flashcards

Gravitation Flashcards

1
Q

Newton’s law of _______ describes ________ ________ between any two objects.

A

gravitation
gravitational attraction

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2
Q

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.

A

directly
product
inversely
square

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3
Q

Any two particles attract each other through __________ forces which are ________ in magnitude even if particles have ________ masses.

A

gravitational
equal
different

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4
Q

If distance between two particles is doubled, the gravitational force between them is _________ as great.

A

1/4

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5
Q

The equation for weight is _________.

A

w = m*g

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6
Q

For any objects that have spherically symmetrical mass distributions, they can be modelled as if ____________________.

A

mass was concentrated at center.

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7
Q

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 _________.

A

decreases
zero

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8
Q

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.

A

spherical
heavier
lighter

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9
Q

Use __________ to determine gravitational constant G.

A

Cavendish torsion balance

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10
Q

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.

A

vectorially
vector sum

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11
Q

_________ 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.

A

Newton’s third law
different

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12
Q

________ holds earth together and keeps planets in orbit around the sun.

A

gravity

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13
Q

______________ 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.

A

mutual gravitational attraction

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14
Q

The formula for acceleration is ____________.

A

a = Fg/m

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15
Q

______ of an object is the total gravitational force exerted on the object by all other objects in the universe.

A

weight

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16
Q

the equation for weight is ________ or _______.

A

w = Fg = (GmEm)/RE^2
w = m*g

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17
Q

The equation for acceleration due to gravity is __________. It is ____________ of mass.

A

g = (G*mE)/RE^2
independent

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18
Q

The equation for weight of an object at a distance from center of the earth is given by _________.

A

w = Fg = (GmEm)/r^2

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19
Q

Weight of an object _______ inversely with the square of its distance from the earths center.

A

decreases

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20
Q

The apparent weight of an object _______ _______ from gravitational force because earth rotates and is not precisely an inertial frame of reference.

A

differs slighly

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21
Q

The equation for volume of a sphere is __________.

A

VE = 4/3 * pi * RE^3

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22
Q

Gravitational potential energy is proportional to _______ while potential energy is proportional to ________.

A

1/r^2
1/r

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22
Q

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 ________.

A

negative
increases
positive
decreases

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23
Q

U is zero when object of mass m is ___________ the earth.

A

infinitely far from

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24
Q

Total mechanical energy of the system of earth and object is ________/_________.

A

constant
conserved

25
Q

______ 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.

A

closed
open

26
Q

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.

A

earths gravitational attraction
uniform

27
Q

In a circular orbit the speed is just right to keep the distance from the satellite to the center of the earth ________.

A

constant

28
Q

Relationship between orbit radius and speed mean _______ choose them independently.

A

cannot

29
Q

Motion of a satellite ________ on mass.

A

does not depend

30
Q

Apparent weightlessness occurs when _______________.

A

gravity is the only force acting on a spacecraft.

31
Q

True weightlessness occurs if an astronaut is __________ from any other masses and gravitational force is _________.

A

infinitely far
zero

32
Q

Larger orbits correspond to __________ speeds and ________ periods.

A

slower
longer

33
Q

Escape speed from a spherical object with radius R is __________ than speed of a satellite in a circular orbit at that radius.

A

sqrt 2 times greater

34
Q

Total mechanical energy in a circular orbit is ________ and equal to ________ the potential energy. Increasing orbit radius means _________ total mechanical energy.

A

negative
0.5
increasing

35
Q

The larger the radius of a satellites orbit, the ________ the total mechanical energy, the _________ the potential energy, and the _________ the kinetic energy.

A

greater
greater
smaller

36
Q

Kepler’s first law states that each planet moves in _________ orbit, with the sun at one focus of the ________.

A

elliptical
ellipse

37
Q

Kepler’s 2nd law states: a line from the sun to a given planet sweeps out ________ areas in _______ times.

A

equal
equal

38
Q

Kepler’s 3rd law states: the periods of the planets are proportional to the _________ powers of the major axis lengths of their orbits.

A

3/2

39
Q

________ is a measure on how intense the ellipse is. At e=_____ the ellipse is a circle.

A

eccentricity
0

40
Q

The point in the planet’s orbit closest to the sun is the _________ and the point most distant is the __________.

A

perihelion
aphelion

41
Q

Closed orbits have shape ______ or ______. Open orbits have shape _______ or _______.

A

circle
ellipse
parabolas
hyperbolas

42
Q

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 ________.

A

same value
small
large
large
small

43
Q

Period _______ depend on eccentricity.

A

does not

44
Q

Sun ______ stationary because of ___________.

A

is not
gravitational force of same magnitude but opposite direction

45
Q

_______ of a star can help discover other plants in orbit around other stars.

A

wobble

46
Q

__________ is the idea that objects in celestial realms obey the same laws of motion as objects on earth.

A

newtonian synthesis

47
Q

Earth is not precisely an inertial frame of reference because it ___________.

A

rotates on its axis

48
Q

Apparent weight of an object on earth is ____________ to the earth gravitational attraction.

A

not precisely equal

49
Q

The earths gravitational attraction is the __________ of an object.

A

true weight

50
Q

Apparent weight is the same as true weight at _________ or __________.

A

north pole
south pole

51
Q

Except a poles, the apparent weight is _______ than the gravitational force of attraction on the object.

A

less

52
Q

Because earth is rotating, a falling object at equator has acceleration _________. If earth was not rotating the object would have free fall acceleration __________.

A

g0 = w0/m
g = w/m

53
Q

If a spherical nonrotating object with mass M hs radius ______ Rs, then nothing can escape the surface of the black hole.

A

<=

54
Q

The surface of the sphere with radius Rs surrounding a black hole is the __________ as we cannot __________.

A

event horizon
observe events occurring inside

55
Q

From outside the even horizon all an observer can know about a black hole is ________, __________ and ________.

A

mass, electric charge, angular momentum.

56
Q

Closer to a black hole clocks run ______, an effect called _______.

A

slower
time dilation

57
Q

___________ theorized that planets orbit around the sun (_________ model) in circular orbits.

A

Copernicus
heliocentric

58
Q

The __________ is a circular orbit that itself moves in along a much larger circular orbit. This is a ________ orbit.

A

epicycles
copernicus

59
Q

The _________ orbit is a circular orbit that itself moves in an _________ orbit.

A

PHYS 124 (3 decks)

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