PHY C8: Gravitational Field Strength

What is a Gravitational Field?

A region of space in which a mass placed in that region experiences a gravitational force.

How is a Gravitational Field visualised?

As consisting of an array of imaginary field lines.

What does the direction of Gravitational Field Lines indicate?

The direction of the gravitational field.

What does the density of Gravitational Field Lines indicate?

Its strength (closer/denser lines = stronger field).

How are field lines directed for a point mass or uniform spherical mass?

Towards its centre.

What is the nature of the gravitational field near the surface of the Earth?

Approximately uniform (field lines seem parallel and evenly spaced).

What is Gravitational Field Strength (g)? (Definition)

The gravitational force experienced per unit mass at that point.

What is the formula for Gravitational Field Strength (g)?

g = F/m.

What is the formula for Gravitational Field Strength due to a Point Mass (M)?

g = GM/r².

Is Gravitational Field Strength a scalar or vector quantity?

Vector quantity.

What are other names for Gravitational Field Strength?

Gravitational acceleration or free fall acceleration.

What is the SI unit for Gravitational Field Strength?

N kg⁻¹ or m s⁻².

In what direction does Gravitational Field Strength point?

Towards the mass which created it.

How is the resultant field strength found at a point due to more than one mass?

From the vector sum of individual gravitational field strengths.

How does Gravitational Field Strength vary inside a uniform solid sphere (r ≤ R)?

It varies linearly with distance r from the centre (g ∝ r).

How does Gravitational Field Strength vary outside a uniform solid/hollow sphere (r > R)?

It varies inversely with r² (g ∝ 1/r²), as if all mass is concentrated at the centre.

What is the Gravitational Field Strength inside a hollow sphere?

Zero.