1.2 Motion: Comparing Weight and Mass using a Balance

This section focuses on understanding the relationship between weight and mass, and how a balance can be used to compare them.

Mass and Weight: Definitions

Mass is a measure of the amount of matter in an object. It is an intrinsic property of an object and remains constant regardless of location.

The SI unit of mass is the kilogram (kg).

Weight is the force exerted on an object due to gravity. It depends on both the mass of the object and the acceleration due to gravity.

The SI unit of weight is the Newton (N), which is a unit of force.

The relationship between mass (m), acceleration due to gravity (g), and weight (W) is given by the equation:

$$W = mg$$

Comparing Mass using a Balance

A balance is an instrument used to compare the masses of two objects. There are different types of balances, but the principle remains the same: it compares the weight of the two objects.

A common type of balance is a beam balance, which consists of a beam supported at its center by a pivot.

How to Use a Beam Balance

1. Place the objects to be compared on the two arms of the balance.
2. Add or remove weights from the lighter side until the beam is horizontal.
3. When the beam is horizontal, the masses of the two objects are equal.

Table: Types of Balances and their Principle

Type of Balance	Principle
Beam Balance	Compares the weights of two objects by observing the position of a pivot.
Spring Balance	Measures weight by the extension of a spring. The extension is proportional to the weight.
Electronic Balance	Uses electronic sensors to measure the force exerted by an object and converts it to a mass reading.

Important Considerations

When using a balance, it's important to ensure that the balance is level and that the objects are placed symmetrically on the arms to avoid errors.

The acceleration due to gravity (g) is approximately 9.8 m/s² near the Earth's surface, but this value can vary slightly depending on location.