Difference Between Mass and Weight - Key Physics Concepts

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People often use the words “mass” and “weight” interchangeably when talking casually, but these two terms have different meanings. The difference between mass and weight lies in this: mass tells us how much matter is in an object, while weight reveals how gravity pulls on that matter.

Mass tells us how much matter is in an object and is represented by the letter m or M.
Weight, on the other hand, is the force of gravity pulling on that mass. We often use the letter W to show weight, and it’s calculated by multiplying the mass by the strength of gravity (g).

W = m x g

Definition of Mass

To put it more simply, mass means how much matter is in an object. It’s like counting the protons, neutrons, and electrons inside it. Mass tells us how hard it is to make something speed up or slow down when we push or pull on it. We usually use kilograms and grams to measure mass.

Definition of Weight

The weight of an object is the force caused by gravity pulling on it. Some folks describe it as a vector, which means it has both direction and size – that’s the gravitational force acting on the object. Others describe it as a scalar, which is just the size or magnitude of that gravitational force. Basically, when things with mass interact with the Earth, this force we call weight comes into play. We measure weight in units called Newtons or pounds.

Difference Between Mass & Weight

Mass is a fundamental measurement of how much matter an object contains. Weight is a measurement of the gravitational force on an object

S. No.	Differentiating Property	Mass	Weight
1	Definition	Mass is simply the measure of the amount of matter in a body.	Weight is the measure of the amount of force acting on a mass due to acceleration due to gravity.
2	Denotation	Mass is denoted by “M”.	Weight is denoted by “W”.
3	Formula	Mass is always constant for a body and there are several formulas to calculate mass. One way to calculate mass is: Mass = volume × density	Weight is the measure of the gravitational force acting on a body. Weight can be calculated from the following formula: Weight = mass × acceleration due to gravity
4	Quantity Type	Mass is a base quantity. Mass only has magnitude and so, it is a scalar quantity.	Weight is a derived quantity. Weight has both magnitude and direction (towards the centre of gravity) and so, it is a vector quantity.
5	Unit of Measurement	The SI unit of mass is Kilogram (Kg).	The SI unit of weight is Newton (N).
6	Gravitational Effect	Mass does not depend upon gravity and is constant everywhere. Mass can never be zero.	Weight is dependent on gravity and so, it varies from place to place. Weight can be zero where there is no gravity (like space).
7	Measuring Instrument	Mass can be easily measured using any ordinary balance like beam balance, lever balance, pan balance, etc.	Weight can be measured by a spring balance or by using its formula.

These represent the key differences between mass and weight, which often confuse students. Understanding this topic thoroughly is vital, as it plays a significant role in the field of physics mechanics. Frequently, competitive exams include questions related to the disparities between mass and weight as well.

Also Check: Mass Formula & Weight Formula

Difference between Mass and Weight Class 9

In Class 9, you learn that mass and weight are two distinct concepts in physics:

Mass

Mass is the amount of matter or substance present in an object.
It is measured in kilograms (kg) or grams (g) using a balance or scale.
Mass remains constant regardless of an object’s location; it is an intrinsic property.
Mass is a scalar quantity, meaning it has magnitude but no direction.

Weight

Weight is the force exerted on an object due to gravity.
It depends on both the mass of the object and the strength of the gravitational field where it is located.
Weight is measured in newtons (N) or pounds (lb).
Weight can vary depending on the location of the object; it is not an intrinsic property.
Weight is a vector quantity, which means it has both magnitude and direction (towards the center of the Earth).

Did you Know?

The weight of an object can seem to go up or down when it’s in a liquid, but its actual amount of stuff, or mass, stays the same. If we were somehow in a place without Earth’s air, everything would be a bit heavier, but we wouldn’t be around to check it!

Things have different weights on different planets because the strength of gravity isn’t the same everywhere. For example, an astronaut would weigh less on the Moon compared to being on Earth.

When something is floating on a liquid or an astronaut is in space, it doesn’t have any weight at all. This happens because how much stuff is in an object, its mass, depends on how much space it takes up. Weight, on the other hand, tells us how strongly gravity pulls on it, as explained by the law of gravity. On Earth, our weight is determined by how strongly Earth pulls us toward the ground. Since we don’t weigh the same at the top of a mountain as we do at sea level, we use worldwide standards to avoid making mistakes because of these small differences.

However, it’s interesting to note that our bodies weigh less in water because of something called buoyancy, which is a force pushing upward that balances out gravity’s pull.

FAQs on Difference Between Mass & Weight

What is the Difference between Mass and Weight?

Mass refers to how much matter is in an object, like the number of particles it has. Weight, on the other hand, tells us how gravity pulls on that mass inside the object.

What is the Difference between Mass and Weight in Physics?

In the field of physics, we use the term 'mass' to describe how much stuff is in an object, like how heavy it is. On the other hand, 'weight' is the pull of gravity on an object, making it feel heavy. Mass is a basic way to measure things, while weight tells us how much force gravity applies to them.

Is kg a mass or weight?

The kilogram is the SI Unit for mass in the metric system, and it's widely accepted worldwide. When we talk about the force or weight of an object in the metric system, we use the Newton as the unit. For example, on Earth's surface, 1 kilogram of mass weighs about 9.8 Newtons under normal conditions.

How are mass and weight related?

Mass and weight have a connection, but they aren't identical. Weight comes from both an object's mass and how fast it falls due to gravity.