Gravitational Forces

Key Terms

Gravity: A force of attraction between all mass, particularly evident between large bodies such as the Earth and Moon.
Mass: The amount of matter in an object. Immune to changes in volume or density.
Weight: The force of gravity acting on a mass. Changes with the strength of the gravitational field.
Gravitational field strength (g): The force of gravity per unit mass at a point in a gravitational field.

Every object in the universe attracts every other object with a force directed along the line of centres for the two objects.
This force is proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between the centres of the two objects.
The mathematical representation is: F = G(m1 * m2) / r^2
- F is the force of gravity (measured in newtons)
- G is the gravitational constant
- m1 and m2 are the masses of the objects
- r is the distance between the centres of the two objects

An object’s weight refers to the force with which it is pulled toward the centre of the Earth due to gravity.
The weight can be calculated using W = mg, where:
- W is weight (measured in newtons)
- m is the mass of the object (measured in kilograms)
- g is the gravitational field strength (measured in N/kg)
On Earth, g is approximately 9.81 N/kg. Therefore, an object with a mass of 1 kg has a weight of 9.81 N on Earth.

Gravitational field strength is the force of gravity per unit mass.
It varies based on location, being strongest at the surface of an object and decreasing as you move further away.
The formula to compute gravitational field strength is: g = F/m, where:
- g is the gravitational field strength (measured in N/kg)
- F is the gravitational force (measured in newtons)
- m is the mass of the object experiencing the force (measured in kilograms)

Gravitational forces are fundamental to many aspects of everyday life and scientific study, from how objects fall to the ground to the prediction of planetary orbits.
Understanding gravity and its effects can help solve real-world problems, such as the construction of buildings and bridges, and it also forms the basis for exploring other areas of physics, such as relativity.