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Physics > Gravitational Fields (UNFINISHED) > Flashcards

Gravitational Fields (UNFINISHED) Flashcards

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1
Q

What is a force field

A

A region in which a body experiences a non-contact force

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2
Q

How are force fields represented

A

As vectors

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3
Q

How do force fields arise

A

From the interactions of mass. static charge and between moving charges

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4
Q

What are the similarities between gravitational and electrostatic forces

A

Both have inverse square force laws that have many common features such as :

use of field lines
use of potential concepts

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5
Q

What are the differences between gravitational and electrostatic forces

A

Masses always attract but charges may attract or repel

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6
Q

What is gravity

A

A universal attractive force acting between all matter

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7
Q

gravitational field strength at a point =

A

force due to gravity (weight) / mass

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8
Q

what does the equation g = F/m show

A

The larger the mass of an object, the greater its pull on another object

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9
Q

What factors affect the gravitational field strength at the surface of a planet

A

The radius/diameter of a planet

The mass of the planet

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10
Q

What is the direction of a gravitational field represented by

A

Gravitational field lines

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11
Q

In what direction do gravitational field lines around a point mass act

A

Radially inwards

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12
Q

How are gravitational field lines of a uniform field represented

A

By equally spaced parallel lines

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13
Q

What are radial/non-uniform fields

A

When the gravitational field strength is different depending on how far you are from the centre

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14
Q

What is a uniform sphere

A

One where its mass is distributed evenly

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15
Q

How do the gravitational field lines around a uniform sphere and a point mass compare

A

They are identical

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16
Q

How do the directions of the field lines differ for radial and uniform fields

A

Radial fields : Towards the centre of the sphere or point charge

Uniform fields : Towards the surface of the object

17
Q

What is the mass of a uniform sphere considered to be at its centre

A

A point mass at its centre

18
Q

Newtons law of Gravitation

A

The gravitational force between 2 point masses is proportional to the product of the masses and inversely proportional to the square of their separation

19
Q

Gravitational force between two masses =

A

Newtons gravitational constant x point mass(1) x point mass (2) / distance between the centres of the 2 masses ^2

20
Q

gravitational field strength in a radial field =

A

G x M / r^2

21
Q

What would the graph of g against r look like

A

When r < R (the radius of the planet) g is directly proportional to r

When r > R, g is inversely proportional to r^2

22
Q

What is GPE

A

The energy an object has when lifted off the ground

23
Q

What is the GPE on the surface of the Earth

A

0

24
Q

What is GPE outside Earth’s surface

A

The energy an object possesses due to its position in a gravitational field

25
Q

What is gravitational potential at a point also know as

A

the gravitational potential energy per unit mass at that point

26
Q

Definition of gravitiational potential energy per unit mass at that point

A

The work done per unit mass in bringing a test mass from infinity to a defined point

27
Q

Why is gravitational potential always a negative value

A

It is defined as 0 at infinity

Since the gravitational force is attractive, work must be done on a mass to reach infinity

28
Q

Why do two points at different distances from a mass have different gravitational potentials

A

The gravitational potential increases with distance from a mass

29
Q

gravitational potential difference =

A

final gravitational potential - initial gravitational potential

30
Q

Gravitational potential, V =

A
  • GM / r
31
Q

Why is the gravitational potential always negative near an isolated mass such as a planet

A

The potential when r is at infinity is defined as 0

Work must be done to move a mass away from a planet

32
Q

What happens to gravitational potential when a mass is closer to a planet

A

Becomes smaller (more negative)

Physics (12 decks)

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