(2) \(\frac{2GM}{\pi R^2}j\)
Consider the semi-circle as made up of large number of point masses (identical). The magnitude of dI is same but direction is different. The total intensity I = ∫ dl
Resolve dI and dI' into rectangular components along x and y–axis. The x–components cancel and y– componant and up.
There resultant intensity I is along y–axis. Also