Question

Suppose the gravitational force between two spheres is $30N$. If the magnitude of each mass doubles, what is the force between the masses?

• A. $80N$
• B. $150N$
• C. $300N$
• D. $120N$

Answer 1

The correct option is D $120N$

From newtons law of gravitation,
$F=\frac{G{m}_1{m}_2}{r^2}$
Initially,
$F_1=\frac{G{m}_1{m}_2}{r^2}=30N$ and $F_2=\frac{G{m}_1^{\prime }{m}_2^{\prime }}{r^2}$
Here, $m_1^{\prime }=2m_1$ and $m_2^{\prime }=2m_2$
therefore, $F_2=\frac{G\times 2m_1\times 2m_2}{r^2}$
or, $F_2=4F_1=4\times 30N=120N$