Hey guys, here we are going to study the most interesting article, which is also applicable in our day to day routine. During health check up doctor suggested to measure your weight by standing on weighing machine, but weighing machine really measures your weight or something else? Its strange that we don’t measure our weight using weighing machine, then we measure exactly? Let’s clear this confusion, by learning the difference between mass and weight.
Mass: Mass is the total amount of matter present in the given substance. Mass of substance always remains same. So if we shift to other planet also, till our mass is going to be unchanged. Mass is independent of direction hence it’s a scalar quantity. SI unit of mass is kilogram (kg) and CGS unit is gram (g).
Weight: Weight is the force that acts on body due to gravity. According to Newton’s second law of motion we have,
Force = mass × acceleration= ma…………………..(1)
The acceleration which gain by body due to gravity is termed as acceleration due to gravity and denoted by ‘g’. Hence equation (1) can be written as,
Force, F= mg…………………………….(2)
This force is nothing but the gravitational force act on body known as weight of body. Therefore,
Weight, W= mg
Weight of body is then product of its mass and acceleration due to gravity at the given point.
Since weight depends on the magnitude acceleration due to gravity ‘g’ it changes from place to place. For e.g. weight of body on earth is maximum at poles whereas its minimum at equator. Weight has directive property hence it is a vector quantity. SI unit of weight is same as that of force i.e. newton (N)and CGS unit is dyne.
Hence from above discussion we can need to change one of our habits to start saying mass of body instead of weight for objects like vegetables, grocery, and weight of person. Means when we say that I have purchased the potatoes of weight 2 kg, then its not the weight that we purchase, its just the mass. The weight of 2 kg potatoes on the earth will be around 20 N as per formula.
Ex: 1. Mayank is having weight of 250 N on earth. What is mass of Mayank? (g = 10 m/s2)
Ans: here W= 250 N
We have
W= mg
m= W/g= 250 / 10 = 25 kg.
Mass of Mayank is 25 kg.
Ex: 2. Mayank having mass of 30 kg travels to moon where the acceleration due to gravity is 1/6th of that of earth. What will be his mass and weight?(g=9.8 m/s2)
Ans: here. m= 30 kg
Mass of object remains same throughout; hence mass of Mayank on moon will be 30 kg.
Now,
gmoon=gearth/6
Wmoon= m × gmoon
Wmoon= 30 × (gearth/6)
Wmoon= 30 × (9.8 / 6)
Wmoon= 49 N