Grav Fields P2 Flashcards

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1
Q

What is the magnitude of the gravitational force of two objects proportional to?

A

The mass of both objects

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2
Q

What is the magnitude of the gravitational force of two objects inversely proportional to?

A

The distance from the centre of both objects squared (Inverse square law)

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3
Q

What is a point mass?

A

Where the mass is concentrated at a single point

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4
Q

What is gravitational field strength?

A

The gravitational force per unit mass of a test mass

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5
Q

What is a test mass?

A

A particle with a very small mass used to test a gravitiational field without affecting it

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6
Q

What is gravitational potential energy?

A

The amount of energy/work done required to move a mass from infinity to a given point in a gravitational field

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7
Q

What is gravitational potential energy at infinity?

A

Zero

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8
Q

What happens to the GPE as it gets closer to the source mass?

A

The more negative the GPE becomes

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9
Q

What is escape velocity?

A

The minimum velocity required for an object to move from a point in a planet’s gravitational field to a point where the gravitational field is negligible.

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10
Q

What is gravitational potential?

A

The work done to move a 1kg mass from infinity to a point in the field

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11
Q

What are equipotentials?

A

A set of points which have the same gravitational potential

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12
Q

What is potential gradient?

A

The change in potential per unit distance at that point.

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13
Q

What does the area between two points below a gravitational field strength graph tell us?

A

The gravitational potential difference

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14
Q

At what seperations are equipotentials when the gravitational field strength is high?

A

Large seperations

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15
Q

What do satellites do in low Earth orbits?

A

They move over lots of different points on the surface and orbit relatively close to the surface

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16
Q

What do satellites do in geostationary orbits?

A

They appear to stay still in the sky over a single point on the surface and orbit at distances relatively far from the surface

17
Q

How do you derive the escape velocity?

A

Set the equations of kinetic energy and gravitational force equal to each other

18
Q

What is the formula for the total energy of a satellite?

A

-GMm/2r

19
Q

Why is gravitational potential difference a negative value?

A

Because work needs to be done to move an object from the inside of the field to the outside. Since infinity is zero, below infinity must be negative

20
Q

How is the orbital period realted to the radius of a circular orbit?

A

T^2 = k x r^3

21
Q

How could you find the speed of an orbiting satellite?

A

Set the centripetal force to the gravitational force and sub in v=2πr/T

22
Q
A