Question

Masses $2kg$ and $8kg$ are $18cm$ apart. The point where the gravitational field due to them is zero is:

• A. $6cm$ from $8kg$ mass
• B. $6cm$ from $2kg$ mass
• C. $1.8cm$ from $8kg$ mass
• D. $9cm$ from each mass

Answer 1

The correct option is B $6cm$ from $2kg$ mass

$m_1=2,m_2=8,r=0.18$

Let point of zero potential be at $x$ from $m_1$.

Balancing the gravitational potential,

$\frac{G{m}_1}{x^2}=\frac{G{m}_2}{(r-x{)}^2}$

$x=\frac{d}{\sqrt{\frac{m_2}{m_1}}+1}$ from the lesser mass

On solving, $x=6cm$ from $2kg$ mass.