Physical quantity of mass is kilo gram and weight is Newton but generally we say my weight is some x kg why so why does this confusion if I was not wrong weight=mass*acceleration due to gravitation But some of the physics books also I find this mistake they ask if a man weights 60 kg on earth what is his weight on moon the answer is 10 kg the explanation is moons acceleration is 1/6 of acceleration due gravity on earth please explain.
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Actually, weight by definition, is the force with which the earth pulls you down. Hence, its units are newton (since it is a force) or $\mathrm{kgf}$ (kilogram force). Now here's how to understand the difference between the two. My mass is $m$, hence my weight $W$ by definition is the force with which the earth pulls me down $$W=\frac{GmM}{R^2}=m\times\left(\frac{GM}{R^2}\right)=m\times g$$ Here $G$ is the universal gravitational constant, $M$ is the mass of the earth, $R$ is the radius of the earth and $g$ is the acceleration due to gravity. So, my weight is either $mg$ newtons or $m$ $\mathrm{kgf}$. Here the acceleration due to gravity $g$ is boycotted because the comparisons of weight are usually made only on the surface of the earth, hence since the $g$ factor scales it linearly, comparisons can be made outside or without it. This local lingo of calling the weight as $m\ \mathrm{kgf}$ is generally called as $m\ \mathrm{kg}$. So, the weight of the man on Earth is $W=60\times g = 60g = 60\ \mathrm{kgf}$, whereas for a man on the moon, $W=60\times\frac g6= 10g =10\ \mathrm{kgf}$, hence in local lingo $10\ \mathrm{kg}$.
Ghosal_C
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Kilogram is a mass unit. In common language the weight is often given in kilograms or pounds which actually are mass units. The reason is the equivalence of gravitational mass (which is proportional to the force in a gravitational field) and the inertial mass. So you know that the force of $F=1\ \mathrm{kg}\times9.81\ \mathrm{m/s^2}=9.81\ \mathrm N$ corresponds to the force exerted by Earth's gravitation on a mass of $1\ \mathrm{kg}$ at sea level.
freecharly
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