Question

What is the weight of a man whose mass is $80\,Kg?$
A. $8.1\,N$
B. $70.2\,N$
C. $80\,N$
D. $89.8\,N$
E. $784\,N$

Answer 1

In order to calculate the weight of man whose mass is given to us $80\,Kg$ , firstly we will learn basic concept behind terms mass and weight and then by using the general formula of weight of a body, we will solve this question for the correct answer. and we should also know that from Newton's law that force is the product of mass and acceleration of the body.

Complete step by step answer:
In physics, mass is the fundamental property of all the matter which is present in the universe, mass is the total amount of composition of a matter. The basic unit in which mass is measured is Kilogram. Weight is defined as the force acting on a body which has some definite mass and the force acting on it due to acceleration produced by gravity.

So, From Newton’s law we know that force is the product of mass and acceleration of the body and weight is the force due to acceleration due to gravity hence for earth the value of acceleration due to gravity is $g = 9.8\,m{s^{ - 2}}$ and the mass of a man is given to us $m = 80\,Kg$ hence, weight of a man is calculated as
$W = mg$
$\Rightarrow W = 80 \times 9.8\,Kgm{s^{ - 2}}$
$\therefore W = 784\,N$
So, the weight of a man whose mass is $80\,Kg$ is $W = 784\,N$.

Hence, the correct option is E.

Note: It should be remembered that, mass and weight are sometimes misunderstood that they are both same quantity so always remember, mass don’t change with respect to position of a body in the space but weight always change of a body in space for example acceleration due to gravity on moon is less than that of earth so a same massive body will have less weight on moon as compared to that of on earth.