A force field is a region of space where a body experiences a non-contact force .

Define non-contact force .

A non-contact force is a force that acts without physical contact between two bodies, e.g. a magnet attracting a metal object.

A field line (or line of force) is an arrow that shows the direction of a force field .

What type of particle experiences a force in a gravitational field ?

Any particle with mass experiences a force in a gravitational field.

What does the direction of a force-field vector at a point represent?

The direction of the force that would be exerted on a body if it were placed at that point in the field.

Static or moving charged particles experience a force in an .......... field, but only moving charged particles experience a force in a .......... field.

Static or moving charged particles experience a force in an electric field, but only moving charged particles experience a force in a magnetic field.

True or False? A stationary charged particle experiences a force in a magnetic field.

False. Only a moving charged particle experiences a force in a magnetic field ; a stationary charge experiences no magnetic force.

Define gravitational field .

A gravitational field is a region of space where a mass experiences a force due to the gravitational attraction of another mass.

Are gravitational forces ever repulsive?

No, gravitational forces cannot be repulsive — they are always attractive.

What is the range of the gravitational force?

Infinite — gravity affects all objects in the universe.

Name two factors that affect the gravitational field strength at the surface of a planet.

The radius (or diameter) of the planet The mass (or density) of the planet

An object has the same mass on Earth and on Jupiter, yet its weight is much greater on Jupiter. Explain why.

Weight depends on the gravitational field strength g , which is greater on Jupiter than on Earth, whereas an object's mass stays the same at all points in space.

The direction of a gravitational field is always towards the .......... of the mass.

The direction of a gravitational field is always towards the centre of the mass.

True or False? g and G represent the same physical quantity.

False. g is the gravitational field strength (N kg -1 ), while G is Newton's gravitational constant — the two must not be used interchangeably.

Under what two conditions can an object be treated as a point mass ?

It has an even mass distribution The distance being considered is larger than its size

What shape are the gravitational field lines around a point mass?

They are radially inward , converging towards the centre.

What do the field lines of a uniform gravitational field look like?

Equally spaced, parallel lines , e.g. near the Earth's surface.

Why is a radial gravitational field described as non-uniform ?

Because the gravitational field strength g is different depending on how far a point is from the centre of the mass.

For a point outside a uniform sphere, the sphere's mass may be considered to act as a .......... at its centre.

For a point outside a uniform sphere, the sphere's mass may be considered to act as a point mass at its centre.

True or False? Gravitational field lines can point away from the mass producing the field.

False. Gravitational forces are attractive only , so field lines always point towards the centre of the mass producing the field.

Define Newton's law of gravitation .

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

In Newton's law of gravitation, what does r represent?

The distance between the centres of the two masses — not the distance between their surfaces.

Under what conditions can large bodies such as stars and planets be treated as point masses ?

They are approximately uniform spheres Their separation is much larger than their radii

True or False? Doubling the distance between two masses halves the gravitational force between them.

False. Gravitational force follows an inverse square law , so doubling the distance reduces the force to one quarter of its original value.

What is the value of the gravitational field strength g at the Earth's surface?

A constant value of 9.81 N kg -1 .

How does g vary with distance r outside a planet ( r > R )?

g is inversely proportional to r 2 — it decreases rapidly as r increases (an inverse square law).

How does g vary with distance r inside a uniform planet ( r < R )?

g is directly proportional to *r *.

What is g also known as, and what are its alternative units?

The acceleration due to gravity , with units m s -2 .

The direction of gravitational field strength g is always towards the .......... of the body creating the field.

The direction of gravitational field strength g is always towards the centre of the body creating the field.

True or False? The gravitational field strength g is constant at all points outside the Earth's surface.

False. Outside the Earth's surface, g decreases as r increases following an inverse square law; it is only constant (9.81 N kg -1 ) at the surface itself.

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Gravitational Fields (AQA A Level Physics): Flashcards

Exam code: 7408

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Cards in this collection (34)

Define force field.
A force field is a region of space where a body experiences a non-contact force.
Define non-contact force.
A non-contact force is a force that acts without physical contact between two bodies, e.g. a magnet attracting a metal object.
Define field line.
A field line (or line of force) is an arrow that shows the direction of a force field.
What type of particle experiences a force in a gravitational field?
Any particle with mass experiences a force in a gravitational field.
What does the direction of a force-field vector at a point represent?
The direction of the force that would be exerted on a body if it were placed at that point in the field.
Static or moving charged particles experience a force in an .......... field, but only moving charged particles experience a force in a .......... field.
Static or moving charged particles experience a force in an electric field, but only moving charged particles experience a force in a magnetic field.
True or False?
A stationary charged particle experiences a force in a magnetic field.
False.
Only a moving charged particle experiences a force in a magnetic field; a stationary charge experiences no magnetic force.
Define gravitational field.
A gravitational field is a region of space where a mass experiences a force due to the gravitational attraction of another mass.
Define gravitational field strength, g.
The gravitational field strength g at a point is the force F per unit mass m of an object at that point:
$g = \frac{F}{m}$
Units: N kg^-1
Are gravitational forces ever repulsive?
No, gravitational forces cannot be repulsive — they are always attractive.
What is the range of the gravitational force?
Infinite — gravity affects all objects in the universe.
Name two factors that affect the gravitational field strength at the surface of a planet.
- The radius (or diameter) of the planet
- The mass (or density) of the planet
An object has the same mass on Earth and on Jupiter, yet its weight is much greater on Jupiter. Explain why.
Weight depends on the gravitational field strength g, which is greater on Jupiter than on Earth, whereas an object's mass stays the same at all points in space.
The direction of a gravitational field is always towards the .......... of the mass.
The direction of a gravitational field is always towards the centre of the mass.
True or False?
g and G represent the same physical quantity.
False.
g is the gravitational field strength (N kg^-1), while G is Newton's gravitational constant — the two must not be used interchangeably.
Under what two conditions can an object be treated as a point mass?
- It has an even mass distribution
- The distance being considered is larger than its size
What shape are the gravitational field lines around a point mass?
They are radially inward, converging towards the centre.
What do the field lines of a uniform gravitational field look like?
Equally spaced, parallel lines, e.g. near the Earth's surface.
Why is a radial gravitational field described as non-uniform?
Because the gravitational field strength g is different depending on how far a point is from the centre of the mass.
For a point outside a uniform sphere, the sphere's mass may be considered to act as a .......... at its centre.
For a point outside a uniform sphere, the sphere's mass may be considered to act as a point mass at its centre.
True or False?
Gravitational field lines can point away from the mass producing the field.
False.
Gravitational forces are attractive only, so field lines always point towards the centre of the mass producing the field.
Define Newton's law of gravitation.
The gravitational force between two point masses is proportional to the product of the masses and inversely proportional to the square of their separation.
Write the equation for the gravitational force F between two point masses.
$F = \frac{G m_{1} m_{2}}{r^{2}}$
In Newton's law of gravitation, what does r represent?
The distance between the centres of the two masses — not the distance between their surfaces.
Under what conditions can large bodies such as stars and planets be treated as point masses?
- They are approximately uniform spheres
- Their separation is much larger than their radii
In the equation $F = \frac{G m_{1} m_{2}}{r^{2}}$ , the constant G represents ...........
In the equation $F = \frac{G m_{1} m_{2}}{r^{2}}$ , the constant G represents Newton's gravitational constant.
True or False?
Doubling the distance between two masses halves the gravitational force between them.
False.
Gravitational force follows an inverse square law, so doubling the distance reduces the force to one quarter of its original value.
Write the equation for the gravitational field strength g due to a point mass.
$g = \frac{G M}{r^{2}}$
Where M is the mass producing the field and r is the distance from its centre.
What is the value of the gravitational field strength g at the Earth's surface?
A constant value of 9.81 N kg^-1.
How does g vary with distance r outside a planet (r > R)?
g is inversely proportional to r² — it decreases rapidly as r increases (an inverse square law).
How does g vary with distance r inside a uniform planet (r < R)?
g is directly proportional to *r*.
What is g also known as, and what are its alternative units?
The acceleration due to gravity, with units m s^-2.
The direction of gravitational field strength g is always towards the .......... of the body creating the field.
The direction of gravitational field strength g is always towards the centre of the body creating the field.
True or False?
The gravitational field strength g is constant at all points outside the Earth's surface.
False.
Outside the Earth's surface, g decreases as r increases following an inverse square law; it is only constant (9.81 N kg^-1) at the surface itself.

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