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Mass and Weight

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Last updated date: 26th Apr 2024
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What is Mass?

Mass is the fundamental attribute of any physical body.

All the objects have a matter inside them and the measurement of the matter is the mass. The total mass of the system is assumed to be constant. This means that the mass remains unaffected by the gravitational field strength, regardless of the location, the object or person is in.

The mass has a magnitude that is usually measured in kilograms and grams. Therefore, it is a scalar quantity.

We are on earth and we measure things on earth with earth's gravity.

If your weight is 70 kg which means you weigh 70 kg and the scale would read it 70kg or 154 lbs.


Mass Definition

Mass is defined as the measure of the matter inside a body.

In physics, mass is a quantitative measurement of inertia.

Let’s understand the concept of mass by understanding Newton's second law.

For example, a body of mass, ‘m’ is moving with an acceleration ‘a.’ The force, ‘F’ is applied to the body given by,

F = m . a

Here, mass is a measure of its resistance to acceleration when a force is applied to the body.

Therefore, the greater the mass of a body, the minimum change produced by an applied force.


Mass Meaning

Mass is referred to as the amount of matter contained in a body.

For example, a human body has bones, muscles, tissues, RBC, WBC. As combined, they form a body’s mass.

A person or object may be weightless on the moon because of lack of gravity while he maintains the same mass at all places without considering his location.


Weight Definition

The weight is the amount that something weighs. 

It is defined as the force that acts at all times on the objects near the earth’s surface.

In the field of science and engineering, the weight of an object is related to the force acting on that object, either due to gravity or due to a reaction force that holds it in a place. 

In simple terms, it is the force with which a body is pulled towards the earth.

Therefore, weight is the measure of the heaviness of an object.


Relationship between Mass and Weight

Weight is defined as the force of gravity with which a body is attracted to Earth or another celestial body, and is equal to the product of the object's mass, and the acceleration of gravity given by,

W =  F = mg

The above equation is applicable at all times even when the object is not accelerating. This means the object is under free-fall and no external force other than gravity is acting upon it. 

Here, W is the weight of the body

F = external force

m  = mass of the body

g  = acceleration due to gravity

Here, g is the measure of the intensity of the gravity field in N/kg at any location.

For example, if I weigh 24 kg on earth,  then my mass on the moon will be 1/ 6 to the weight on the earth i.e., 4 kg on the moon.

The mass on the Moon is less than the Earth. However, its gravity is less than the Earth.


Unit of Mass and Weight

In physics, each object has a unit that determines the standard measurement of that body. 

Therefore, a physical quantity such as mass also has a unit. In International systems, SI, the mass is measured in Kilograms denoted by the symbol kg.

Here, weight is a vector quantity measured in Newton, symbolized by N.

Mass vs Weight

Mass 

Weight 

Mass is an attribute referring to the amount of material inside the body.

Weight is the force exerted by gravity on an object (force is caused by gravity pull on the body).

Represented by, ‘m.’

Represented by, ‘mg.’

A scalar quantity (has a magnitude only).

 

A vector quantity (has magnitude and direction) that is directed towards the centre of the earth.

Constant regardless of gravitational field strength.

Varies according to gravitational field strength. 

Mass remains constant at all locations.

Mass increases or decreases with higher or lower gravity.

Mass can never be zero.

Weight can be zero, if the body is in a place with no gravity, such as in space.

Usually measured by analytical balance,  beam balance or calibrated electronic balance.

Measured by spring or compression balance.

Measured in kg or g.

Often measured in Newton (as it is defined as the force of gravity).

Do You know?

Some interesting facts about mass and weight are:

  • The mass does not remain constant.

  • Nuclear reaction: In this reaction, a tiny amount of matter is converted into a large amount of energy, this reduces the mass of the substance.

FAQs on Mass and Weight

1. Can Mass be Created?

Mass can neither be created nor be destroyed. However, it can be changed from one form to another form. For instance, the mass of reactants in a chemical reaction is equal to the mass of products so formed.


Students plan and experiment to establish the Law of Conservation of Mass using Alka-Seltzer and a flask. According to the rule of conservation of mass, mass cannot be created or destroyed. This states that in a chemical process, the total mass of reactants equals the total mass of products.


Students can study mass and the theory of conservation of mass with Vedantu, where the subject specialized teachers of Physics can provide you best guidance to get a complete understanding of the topics, also students get to know some expert tips before appearing in examination that will help you to score extra marks and get good confidence so that students should not panic just before the examination.

2. How Does Volume Affect the Mass?

No effect.


If the volume increases, the mass remains constant. 


For example, I have a metal of mass of 3 gms. The atoms inside this metal are tightly bound and the volume of each atom is just two cubic centimetres. Now if I heat is metal, the volume of each atom expands to 3 cubic centimetres while the mass remains unchanged i.e., 3 gms.


Volume and mass relation can be studied by the students with the professional physics teacher that helps you to clear your concepts well and get prepared for any type of question that can be asked in the examination. Students who want to have a good common of physics chapter mass and weight should study with textbooks as well as the extra material provided by Vedantu that provided all the important questions that can be asked in the examination.

3. Do Photons have Mass?

Light is made of small packets called photons that are massless particles. 

As confirmed experimentally, photons have energy and momentum but don’t have mass.


Therefore it can be said that, because photons travel at the speed of light, the special theory of relativity predicts that they do not have mass. This is also supported by quantum electrodynamics theory, which states that photons cannot have mass due to U(1) -gauge symmetry.


Students can get a deep understanding of this topic with Vedantu. The study material of Vedantu explains photons in a very clear language and you can also study examples that will explain this concept to help you understand it in a better way. Also, students need to study this physics topic for higher competition examination where the questions will be framed in a tricky way to check the students understanding about a certain topic like photons.

4. What is a Relativistic Mass?

Relativistic mass is a special theory of relativity. 


This theory is applied to the objects in motion. The corresponding formulas for the theory are p = mv and  E = mc2. This relativistic mass becomes infinite (because of infinite kinetic energy) when the velocity of the body approaches the speed of light i.e., c. 


The meaning of relativistic is defined as


1. Having to do with, connected to, or characterized by relativity or relativism. 


2. A relativistic electron travelling at a speed that causes a considerable change in characteristics (such as mass) in line with the theory of relativity. 


Other Relativistic Phrases More Sentence Examples Find out more about relativistic thinking. Vedantu helps you to get a detailed study about Relativistic mass and get a good understanding of this topic. This is an important concept and has been asked many times in previous years' exams. Students can check the important questions to know the type of questions that are framed from this topic.

5. Where can I find the best study material for physics Mass and weight?

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