Four particles A, B, C and D with masses mA = m, mB = 2m, mC = 3m and mD = 4m are at the corners of a square. They have accelerations of equal magnitude with directions as shown. The acceleration of the centre of mass of the particles is -
(1) Zero
(2) a (i + j)
(3) a/5(i - j)
(4) a/5(i + j)
