Three solid spheres each of mass m and radius R are released from the position shown in figure. The speed of any one sphere at the time of collision would be
Answer & explanation
Correct answer: option 4
From conservation of mechanical energy
$3\left\{\frac{1}{2} m v^2\right\} = 3\left\{\frac{G m^2}{2 R}-\frac{G m^2}{d}\right\}$
$v^2=G m\left\{\frac{1}{R}-\frac{2}{d}\right\}$
∴ $v=\sqrt{G m\left\{\frac{1}{R}-\frac{2}{d}\right\}}$
Hence, (D) is correct.