Question

Three identical metal balls, each of the radius r are placed touching each other on a horizontal surface such that an equilateral triangle is formed when centres of three balls are joined. The centre of the mass of the system is located at

• A. line joining centres of any two balls
• B. centre of one of the balls
• C. horizontal surface
• D. point of intersection of the medians

Answer 1

Answer: (D)

Centre of mass of each ball lies on the centre.
$\Rightarrow$ Centre of mass of combined body will be at the centroid of equilateral triangle.