Mechanics

# Difference between mass and weight with example

The basic difference between mass and weight is that mass is the amount of matter in an object, while weight is the force of gravity by which earth attracts towards it. Mass is the scalar quantity and weight is a vector quantity. The unit of mass is kg while the unit of weight is N. Unfortunately, weight and mass are often considered to be the same quantities and misused in daily conversations. It is therefore essential for you to differentiate between these two physical quantities.

## 5 differences between mass and weight of a body

Properties of mass

• Mass is the quantity of matter possessed by a body.
• It is a scalar quantity, which has magnitude only.
• Its unit is kilogram (kg).
• It is not changed by changing the position.
• It is calculated by the formula:    m=w/g
• It is measured by physical balance, beam balance, electronic balance, etc.

Properties of weight

• Weight is the gravitational force by which earth attracts towards it.
• It is a vector quantity, which means that it has magnitude and direction.
• Its unit is newton (N).
• It is changed by changing the position.
• It is calculated by the formula: w=mg
• It is measured by a spring balance.

## The relation between weight and mass

Weight and mass are related, bodies having large mass also have large weight. For Example, a large object is hard to throw because of having a large weight.

To understand the relationship between weight and mass, note that a freely falling body has an acceleration of magnitude “g”.From Newton’s second law we come to know that a force must act to produce gravitational acceleration.

For example, if a body of mass 1 kg falls with an acceleration of 9.8 meters per second square, the required force has a magnitude which is given as:

F=ma

=(1kg)(9.8 m/s²)

=9.8kgm/s²

=9.8N

The force that makes the body accelerate downward is known its weight. Anybody near the surface of the earth has a mass of 1kg must have a weight of 9.8 N to give it the acceleration.

## How is weight measured?

A body which has mass m must have weight with magnitude “w” which is measured by the following formula:

w=mg

Hence body’s weight is directly proportional to its mass m. Greater the mass of an object greater will be its weight.

Since weight is vector quantity, therefore we can write the relation to find weight in vector form as:

w=mg

Where g is the magnitude of g, which is acceleration due to gravity.

Related topics in our websites are: