Section 3:
Gravitational and Electrical Fields
Gravitational Fields
Gravitational Field is a force field in a region in which a body experiences a non-contact force
o Force fields arise from interactions between objects or particles e.g. between static or
moving charges, or in the case of gravity, between masses.
Representation of Gravitational fields:
Force fields are represented as vectors, showing the direction of the force they would exert on
an object in the field.
The Earth’s gravitational field is radial. If a small mass is put anywhere in the surface, it will be
attracted towards the center.
The force field line density is more concentrated at the surface. The further we go away from
the surface the less force the object experiences.
Newton’s law of Gravitation:
The force experienced by an object in a gravitational field is always attractive. It depends on the
masses involved and the distance between them – easier to calculate with point masses.
G m1 m2
F=
r2
1. F – is Force
2. G – is Gravitational constant, Nm2kg-2
3. m1 – is the mass of the first object
4. m2 – is the mass of the second
5. r – is the distance between the centre of the two masses
The value for G is 6.67 X 10-11
The Inverse Square law comes into place in Newton’s law of Gravitation:
1
𝐹 ∝
𝑟2
o This law uses inverse square law because it’s radial. The force at any point, r, from the
surface will be the same. If you increase the distance to 2r, then the area covered by the
gravitational force will be 4 times greater, as well as 4 times weaker.
Gravitational and Electrical Fields
Gravitational Fields
Gravitational Field is a force field in a region in which a body experiences a non-contact force
o Force fields arise from interactions between objects or particles e.g. between static or
moving charges, or in the case of gravity, between masses.
Representation of Gravitational fields:
Force fields are represented as vectors, showing the direction of the force they would exert on
an object in the field.
The Earth’s gravitational field is radial. If a small mass is put anywhere in the surface, it will be
attracted towards the center.
The force field line density is more concentrated at the surface. The further we go away from
the surface the less force the object experiences.
Newton’s law of Gravitation:
The force experienced by an object in a gravitational field is always attractive. It depends on the
masses involved and the distance between them – easier to calculate with point masses.
G m1 m2
F=
r2
1. F – is Force
2. G – is Gravitational constant, Nm2kg-2
3. m1 – is the mass of the first object
4. m2 – is the mass of the second
5. r – is the distance between the centre of the two masses
The value for G is 6.67 X 10-11
The Inverse Square law comes into place in Newton’s law of Gravitation:
1
𝐹 ∝
𝑟2
o This law uses inverse square law because it’s radial. The force at any point, r, from the
surface will be the same. If you increase the distance to 2r, then the area covered by the
gravitational force will be 4 times greater, as well as 4 times weaker.
