IGCSE Physics 0625 - 1.2 Motion

Weight: The Effect of a Gravitational Field on a Mass

Weight is the force exerted on an object due to gravity. It is a measure of the gravitational attraction between the object and the Earth (or any other massive body).

Understanding Weight

Weight is a force, and therefore it is measured in Newtons (N). The relationship between weight (W), mass (m), and the acceleration due to gravity (g) is given by the following equation:

$$W = mg$$

Where:

• W is the weight of the object (in Newtons)
• m is the mass of the object (in kilograms)
• g is the acceleration due to gravity (approximately 9.8 m/s² on the Earth's surface)

Acceleration due to Gravity (g)

The acceleration due to gravity (g) is the acceleration that objects experience when falling freely under the influence of gravity. On Earth, this value is approximately 9.8 m/s². This means that the velocity of an object in free fall increases by 9.8 m/s every second.

Factors Affecting Weight

The weight of an object depends on two factors:

1. Mass: The more massive an object, the greater its weight.
2. Acceleration due to Gravity: The acceleration due to gravity varies depending on the distance from the center of the Earth. It is slightly weaker at higher altitudes.

Table Summarizing Weight

Concept	Definition	Formula	Units
Weight	The force exerted on an object due to gravity.	$$W = mg$$	Newtons (N)
Mass	A measure of the amount of matter in an object.	$$m$$	Kilograms (kg)
Acceleration due to Gravity	The acceleration experienced by objects falling freely under gravity on Earth.	$$g \approx 9.8 \, m/s^2$$	m/s2

Suggested diagram: A diagram showing an object with mass 'm' experiencing a downward gravitational force 'W' due to the Earth's gravitational field. Label 'm' as mass, 'g' as acceleration due to gravity, and 'W' as weight.