Three masses each of mass m are palced at the vertices of an equilateral triangles ABC of side l as shown in figure. The force acting on a mass 2m placed at the centroid O of the triangle is

Explanation

`vecF_(GA) = (G(2m)(2m))/(1^2) hatj`
` vecF_(GC) = (G(m)(2m) )/(1^2) ( + hati cos 30^@ - hatj sin 30^@)`
`vecF_(GB) = (G(m)(2m) )/(1^2) ( + hati cos 30^@ - hatj sin 30^@)`
` vecF_G = vecF_(GA) + vecF_(GB) + vecF_(GC) = 4Gm^2 hatj - 2Gm^2 (2 sin 30^@) hatj =2 Gm^2 hatj`