Three objects -- two of mass m and one of mass m -- are located at three corners of a square of edge length ℓ. find the gravitational field g at the fourth corner due to these objects. (express your answers in terms of the edge length ℓ, the masses m and m, and the gravitational constant g). magnitude

The magnitude of the gravitational field is = GM/R^2Where:R = l, and G = gravitation constant, m = mass 

The field strength of the diagonal mass is computed by GM/(l*√2)^2 
And the sum of the field magnitudes from the two neighbored masses is GM*√2/l^2. 

So the total magnitude is computed by: GM/(2l^2) + GM√(2)/l^2