Mention the centre of mass of three particles which are not in line but have equal masses. 

Three point masses $m_1, m_2$ and $m_3$ are placed at the corners of a thin massless rectangular sheet ($1.2 \,m \times$ $1.0 \,m$ ) as shown. Centre of mass will be located at the point ........... $m$

What is centre of mass ?

$Assertion$ : The position of centre of mass of a body depends upon shape and size of the body.
$Reason$ : Centre of mass of a body lies always at the centre of the body.

A square shaped hole of side $l=\frac{a}{2}$ is carved out at a distance $d =\frac{ a }{2}$ from the centre $'O'$ of a uniform circular disk of radius $a$. If the distance of the centre of mass of the remaining portion from $O$ is $-\frac{a}{X},$ value of $X$ (to the nearest integer) is.......

A man inside a freely falling box throws a heavy ball towards a side wall. The ball keeps on bouncing between the opposite walls of the box. We neglect air resistance and friction. Which of the following figures depicts the motion of the centre of mass of the entire system (man, the ball and the box)?