Mass is the amount of matter in an object, while weight is the force of gravity by which the 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.
What is mass?
Mass is the amount of matter that an object has. It is a quantitative measure of a body’s resistance to acceleration. We can see it as the resistance of tableware when the tablecloth is pulled out.
Regardless of where the body is, the mass will always be the same, that is, it is an intrinsic amount of matter.
Mass is an extensive property of matter, it depends on the quantity and size of the system under study. This means that if an object of mass equal to 1 kg, we take away 0.1 kg since the mass will not be equal to the original object.
How is mass measured?
The mass is normally measured by means of a balance, making a comparison with a known standard. In the International System of Units (SI) the mass is expressed in kilogram (kg). As of May 20, 2019, the kilogram is defined in terms of the Planck constant h , a fundamental constant of quantum physics that is universal:
This new kilogram measurement replaces the old definition of the kilogram, based on the prototype of the international kilogram, a cylinder of platinum and iridium that is kept protected by the International Bureau of Weights and Measures in Sèvres, France in 1889.
What is weight?
Weight is the gravitational force exerted by Earth or any other celestial body on an object, which is equal to the product of the object’s mass and the value of the local gravitational acceleration:
The value of the acceleration constant on Earth is 9.8 m / s 2. The formula can interpret that the weight is proportional to the mass of the object.
Weight is a vector quantity since it has the intensity, direction, and sense. As such, weight is a measure resulting from the action that the earth’s gravity exerts on a body, and thus, weight is a variable value.
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 the 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 the earth attracts it.
- It is a vector quantity, which means that it has magnitude and direction.
- Its unit is the newton (N).
- It is changed by changing the position.
- It is calculated by the formula: w=mg
- It is measured by a spring balance.
Difference between mass and weight in tabular form
|It is a scalar Quantity.||It is vector Quantity.|
|The value of the mass remains constant.||The value of weight varies according to the position of an object.|
|It is represented by “m”.||It is represented by “W”.|
|Its SI unit is kg.||Its SI Unit is Newton.|
|It is measured instruments like beam balance.||It is measured instruments like spring balance.|
|Its formula is: m = w/g||Its formula is : W = mg|
Suggested video: Mass Vs Weight
The relation between weight and mass
Weight and mass are related, bodies having large mass also have a 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:
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:
Hence body’s weight is directly proportional to its mass m. The greater the mass of an object greater will be its weight.
Since weight is a vector quantity, therefore we can write the relation to find weight in vector form as:
Where g is the magnitude of g, which is the acceleration due to gravity.
For your Curiosities:
Did you know that by measuring our weight, we actually measure our mass?
When we place ourselves on a scale to weigh ourselves, we usually call that our weight, in reality, we are measuring it is our mass, that is, the amount of matter in our body. There are other machines that can actually measure our weight, these are not so used and work by standing for a moment on them, and in the end, it gives a true weight value also expressed in Newton.
Does the weight vary depending on where we are?
We do not weigh the same on the moon and even in space, where there is no gravity, the mass remains constant but the weight is zero.
The mass is based on the volume that a body occupies, the weight manifests the energy of that object with respect to the attraction that gravity exerts with another object. Weight on land is determined by the force with which the earth draws us to the ground. To be exact, we do not weigh the same at the top of a mountain as at sea level, so worldwide standards have been established to avoid mistakes since the difference is very small.
On the other hand, it is worth noting that our body in water weighs less due to the buoyancy exerted by a force contrary to the force of gravity.
Types of mass and weight
From the scientific point of view, understanding that mass and weight are magnitudes with which the matter contained in a body and the force exerted by gravity on it are respectively measured, the types of these that are best known and used are:
- Atomic mass: The mass of an atom.
- Molar mass: The mass of one mole of a substance.
- Molecular mass: The mass of a molecule of a substance.
- Inertial mass: That physical magnitude that indicates the resistance of a body to a change in speed.
- Body mass: It is the mass of a person’s body.
- Atomic weight: It is the average mass of the atoms of an element.
- Molecular weight: It is the result of the sum of the atomic weights of the elements that make up a compound.
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