# Gravitational fields

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• Created by: argyrou
• Created on: 30-04-18 18:19
What is the equation for gravitational field strength in a uniform field?
g=F/m
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What are the 2 possible units of gravity g?
m/s² or N/kg
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What are equipotentials?
lines of constant gravitational potential
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As you get further away from a radial field, what happens to the field strength and the distance of the equipotentials?
the field become weaker the further away you are from the centre of it and the equipotentiols become further apart because GPE gain is decreasing.
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What is the equation for the gravitational potential gradient?
= v /r
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what is the relationship between gravitational field strength and the gravitational potential gradient?
the potential gradient= v/ r but the gravitational field is negative g=- v/ r
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What is the equation to find the change in gravitational potential energy when moving a point from one gravitational potential points to another?
W=m(V1-V2)
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What is Keplers 3rd law?
r³/T² is the same for all planets showing that they orbit the sun. So, r³ is proprtional to T²
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What is Newtons law of gravitation in words?
the gravitational force F between any 2 points has an attractive force between them, have proportional masses and their force is inversly proportional to the sqaure of their disance apart.
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What is the quation for newtons law of gravitation?
F=Gm1m2/r²
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What is G?
the universal gravitational constant which = 6.67x10-11
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What is the unit of the universal gravitational constant G?
Nm²/kg²
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What is the equation for gravitational potential?
V=-GM/r
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What is the equation for gravitational field strength that uses newtons law of gravitation?
g=GM/r²
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What does the area under a gravity against distance from the centre of the planet represent? (g/r)
Gravitational potential.
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What is the equation for the gravitational field strength on the surface of a planet?
g=g(s)R²/r²
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What is the total energy of an orbiting planet?
Et=Ek+Ep = -Gmm/2r
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Whats an importnat feature about the total energy of an orbiting satellite?
The total energy is always negative!!
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What is a geostationary satellite?
Satellite that orbits Earth directly above the equator so has a fixed time period of 24hours.
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What is the equation for (velocity)² in terms of gravity?
v²=GM/r
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what is the constant from Keplers 3rd law (r³/T²)
r³/T² =GM/4 ²
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What is the definition of escape velocity?
the minimum velocity an object must be given to escape the planet when projected vertically
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what must the escape velocity be larger or equal to in order to escape the planet?
2gr
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Whats special about gravitational potential ina gravitational field and why?
gravitational potential is always negative ina gravitational field because force is always attractive
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## Other cards in this set

### Card 2

#### Front

What are the 2 possible units of gravity g?

m/s² or N/kg

### Card 3

#### Front

What are equipotentials?

### Card 4

#### Front

As you get further away from a radial field, what happens to the field strength and the distance of the equipotentials?

### Card 5

#### Front

What is the equation for the gravitational potential gradient?