Question

The weight of a body is $120N$ on the earth. If it is taken to the moon, its weight and mass will be about (Take g${}_e$ = 10 m/s${}^2$)

• A. $120N,120kg$
• B. $60N,12kg$
• C. $20N,12kg$
• D. $720N,120kg$

Answer 1

The correct option is C $20N,12kg$

It is given that the weight of the object on the earth is $120N$. That is $W\left(e\right)=120N$. Acceleration due to gravity is $10m/s.$
Mass of the object on earth, m(e) is calculated as follows.
We know, $W\left(e\right)=M\left(e\right)\times g$
Therefore, $120N=M\left(e\right)\times 10$. That is, $M\left(e\right)=120/10=12kg$
Thus, the massof the object on earth is $12kg$. We know that the mass of the object remains the same through out the universe. Hence, mass of the object on the moon is also $12kg$.
We know, weight of the object on the moon $=1/6$ of the weight of the object on the earth.
Therefore, $W\left(m\right)=1/6\times W\left(e\right)$
That is, $W\left(m\right)=1/6\times 120N=20N$
Hence, the weight and mass of the object on the moon are $20N$ and $12kg$ respectively.