21 Gravitational Fields Flashcards

(31 cards)

1
Q

Gravitational potential energy Ep

A

At a point in a gravitational field is the work done to move a small object from infinity to that point. The change of gradational potential energy of a mass (m) moved through a height (h) near the Earths surface ΔEp = mgΔh

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2
Q

Gravitational potential v

A

At a point in a gravitational field is the work done per unit mass to move a small object from infinity to the point. At the distance r from the centre of a spherical object of mass (M).

V= -GM/r

(a point is the work done per unit mass to move a small object from infinity to that point)
zero value at infinity

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3
Q

Equipotential

A

A line or surface in the field along which the electric or gravitational potential is constant
(no work is done when moving along a equipotential surfaces )

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4
Q

Gravitational fields strength, g

A

Force per unit mass on a small mass placed in the field

g = F/m ( gravitational force on a small mass)
Distance r from a point mass (M).

g= GM/r^2

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5
Q

radial field

A

a field in which the field lines are straight and converge or diverge as if from a single point

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6
Q

field line (line of force)

A

direction of a field line indicates the direction of the force. an electric field line is the path followed by a free positive test charge. the gravitational field line of a single mass point towards that mass

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7
Q

uniform gravitational field

A

The earth is uniform over a region which is small compared to the scale of the Earth

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8
Q

potential gradient

A

at a point in a field is the change of potential per unit charge of distance along a field line at that point.
potential gradient = - the field strength at any point

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9
Q

keeper’s third law

A

for any planet, the cube of its mean radius of orbit is directly proportional to the square of its time period

R^3 / T^2 = GM/ 4(pi)^2

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10
Q

newton’s law of gravitation

A

the gravitational force F between two point masses M and m at distance r apart

F= GMm/ r^2

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11
Q

escape velocity

A

the minimum velocity an object must be given to escape. from the planet when projected vertically from the surface

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12
Q

gravitational field (g) a vector?

A

yes its a vector

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13
Q

Gravitational Force is a ______ force

A

attractive force

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14
Q

Gravitational fields

A

a region within which an object experience gravitational force
the closer the lines the stronger the field
field strength decreases as the distance from the object increases

g= F/M

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15
Q

r is measured from the ____

A

centre

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16
Q

Orbital speed

A

inversely proportional to the square root of the orbital radius
(so Jupiter travels slower than earth)

17
Q

centripetal force of an orbit

A

GMm/r^2 = mv^2 /r

V^2 = GM /r

18
Q

one complete orbit (equation)

A

T = 2(pi)r / v

use the equation V^2 = GM /r

T^2 = 4(pi)^2r^3 / GM

19
Q

geosynchronous orbit

A

has the same orbit time as the earth (24 hours)

appears stationary when your on earth

20
Q

Rocket launch

A

engine provides a constant force which mean the rocket can go slower because the engine would continue to give you thrust to overcome the gravitational potential energy

21
Q

from what height is the gradational force not 9.81 the right value?

22
Q

Cavendish experiment

A

a acute measurement of G (6.67 *10-11)

23
Q

escape velocity equation

24
Q

Satnav

A

uses synchronised and measure the time difference between the signals form the satellites

25
energy of an orbiting satellite
``` E= -GMm / 2r E= EP+EK ```
26
the negative sign in the equation means
gravity is a attractive force
27
we treat all objects as
point masses
28
gravity field are radical meaning they come together to a
straight line | the pull being directly towards the centre, the closer in you get the stronger the pull
29
gravity
universal attractive force acting between all matter
30
work done in moving mass
W = mV
31
area under graph of g against r
V