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solar system > Earth and Moon > Flashcards

Earth and Moon Flashcards

1
Q

What is the mean distance that the Earth and Moon orbit the sun.

A

149 million km (1 Astronomical Unit)

365.256 days (1 year) to complete an orbit

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2
Q

What size is Earth compared to the moon?

A

81 times more massive and 4 times radius

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3
Q

How many days does it take the moon to orbit the Earth and what is the mean distance? (sidereal period)

A

27.3 days, mean distance of 384000 km.

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4
Q

Define the sidereal period?

A

time taken to complete an orbit with respect to the fixed distant stars

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5
Q

Why does the separation of the moon to the earth vary from 362000-405000 km?

A

the orbit is elliptical

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6
Q

what else does the moon do every 27.3 days?

A

rotates on its axis- to keep same face towards us

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7
Q

How much does the planes of the Earths orbit around the sun and the moons orbit around the earth differ by?

A

5 degrees

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8
Q

what is the Earths spin axis inclined at and what effect does this have on the moon?

A

23.4 degrees

moon reaches diff heights in the night sky at diff times of the year

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9
Q

when is the new moon visible?

A

never- moon is same direction as sun

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10
Q

when is crescent visible?

A

west after sunset or in east before sunrise

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11
Q

when is the first quarter visible and when does it rise?

A

rises at midday, sets at midnight
visible in evening as half phase.
moon 90 degree away from sun

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12
Q

when is the full moon visible?

A

throughout night

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13
Q

when does full moon rise and set?

A

rises at sunset

sets at sunrise

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14
Q

how far away from the sun in degrees is a full moon?

A

180

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15
Q

When is the last quarter moon visible?

A

in morning as half phase

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16
Q

when does last quarter rise and set?

A

rise at midnight, sets at midday

17
Q

how far away from the sun in degrees is a last quarter moon?

A

90

18
Q

how many days does a complete lunar phase take and why?

A

29.5 days because as moon orbits earth, position of sun changes

19
Q

what is a solar eclipse?

A

moon passes in front of sun, blocking light from part or all of sun reaching earth.

20
Q

when can a solar eclipse occur?

A

new moon

21
Q

what is a annular solar eclipse and when does it occur?

A

sun appears as ring (annulus) moon too small to cover sun

22
Q

what is a lunar eclipse?

A

moon enters earth shadow cone preventing sunlight reaching moon, Moon turns coppery red, due to sunlight refracted through earths atmosphere.

23
Q

where is a lunar eclipse visible?

A

anywhere on earth where moon is visible above horizon.

24
Q

when can a lunar eclipse happen?

A

full moon

25
Q

why dont we have eclipses every month?

A

because orbit of the moon about the earth is tilted with respected to that of the sun

26
Q

what is a tide?

A

gravitational force due to a distant object decreases with distance from the object. Body is subjected to stronger pull on side closest to object .

27
Q

what is the difference of gravitational force known as?

A

tidal force

28
Q

what is the equation for tidal force?

A 
Ftidal = 2RGM/d^3
F tidal= tidal force per unit
R= body of radius 
M= another body of mass 
d= distance
29
Q

why does the earth not stretch very much?

A

moons tidal force

rigid

30
Q

why is earths oceans strongly influenced by moons tidal force?

A

oceans are liquid and water can flow when force applied to it

31
Q

how are two tidal bulges formed?

A

the tidal force has a stretching effect along a line between Earth and Moon

32
Q

why does the tidal bulge move around the surface of the earth?

A

due to earths rotation

33
Q

why does Earths surface experience two high tides and two low tides per day?

A

bulge generally aligned toward and away from moon

34
Q

what is a spring tide and why does it occur?

A

when sun and moon are aligned (new moon, full moon) tidal forces of sun and moon add together .

35
Q

what is Neap tides and why do they occur?

A

when sun and moon are perpendicular to each other. (first quarter, last quarter)

36
Q

what is tidal friction?

A

when frictional forces occur between water and land causing a lag in ocean bulge which has breaking effect on earths rotation.

37
Q

What effect does tidal friction have?

A

extracting energy from earth-moon system and expending it as head, Length of day increasing by 1.7 milli-seconds per century and earthmoon separation increasing 3.8cm/year

38
Q

how much more greater does the moon experience tidal force due to the earth than the earth due to the moon? what does this mean?

A

20x

moon slightly elongates along line towards earth and moon rotation rate reduced by tidal forces until equalled orbital period

solar system (9 decks)

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