MASS VS WEIGHT
Mass and weight are two very common terms used in science. Kids often use mass and weight interchangeably but only a few of them know that there is a difference between the two. Yes, you read right, mass and weight are not the same. Let’s learn more.
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Mass is a very important property of materials. While studying science you will often hear that different materials have different mass. But what exactly mass is? So, let’s understand it with this simple exercise –
Get two empty glasses from your kitchen. Both glasses should be of the same size. Fill one of them till the top with sand and the other with water. Now lift each of them one by one. Which one of the two glasses you find is heavier?
You will notice that the glass containing sand is heavier than the glass containing water in it.
The reason behind it is that that sand is a solid and most solids contain more atoms than liquids. So although the size of both glasses is same but glass containing sand in it has more atoms then the glass containing water in it. In other words, we can say glass with sand has more mass in comparison to one with water.
So, mass is a measure of the number of atoms or amount of matter present in an object. If we compare two objects of the same volume then one with more atoms in it will have more mass. SI unit of mass is kilogram (kg).
A simple definition of mass for kids –
Mass is a measure of number of atoms or amount of matter in an object.
Force exerted by an object of fixed mass under influence of gravity is called weight.
WEIGHT = MASS X GRAVITY
Weight being a force, thus its SI unit is ‘Newton (N)’. The gravity of earth exerts the force of about 10 N on the mass of 1 kg. In other words, a body of mass 1 kg will weigh 10 N on earth. However, people often use kilogram (kg) as the unit for weight which is not correct. This confusion arises due to another unit of weight which is ‘kilogram-force (kgf)’, where 1 kgf = 10 N (nearly). So, a body having the mass of 1 kg will weigh nearly 1 kgf or 10 N on earth.
As a value of gravity changes around the earth, thus the weight of the object varies at different places, but its mass remains the same. Usually, variation in gravity at different places on the earth is very less, so people use both terms interchangeably by mistaking them as the same thing. But if we can go to any place outside the earth such as moon then we will notice the difference.
For example – the gravity of the moon is 1/6th that of the earth. So if you weigh 360 N on the earth then you will weigh 360 x 1/6 = 60 N at the moon. However, as your body consists of the same number of atoms at the moon as on the earth thus your mass will remain the same at both places.
A simple definition of weight for kids –
Weight is a force exerted by object of fixed mass under influence of gravity
DIFFERENCE BETWEEN MASS AND WEIGHT
- It is a measure of the number of atoms or amount of matter in an object.
- It is constant for a body and does not change with a place.
- Measured using a beam balance.
- It’s S.I. unit is kilogram (kg).
- It is a force exerted by an object of fixed mass due to gravity.
- It is not constant for a body, but it changes from place to place.
- Measured using a spring balance.
- Its S.I. unit is Newton (N) and other unit is kilogram-force (kgf) where 1 kgf = 10 N (nearly)