Can we write $P = hdg$ for solid pressure? Can we write $P=hdg$ for solid pressure too? Does the iron rod of 1 m height having density 7500 kg/m$^3$ have pressure of $1\times7500\times 10\times(hdg)$? And other way round as well, $P=F/A$ for fluids? Like water of weight 10kg standing on cube of 1m$^2$ cross-section has pressure of $(10\times10)/1$ i.e. $F/A$?
 A: The force per unit area that the iron rod exerts on the horizontal surface it is standing on is indeed given by $p=h\rho g$. But this is likely to be misleading because…


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*It works for a solid only if the mean cross-sectional area as we go up from the base is equal to the area of the base. With a (stationary) liquid it works for any shape of container.

*The pressure at depth $h$ in a stationary liquid is $p=h\rho g\ $ on a surface the liquid is in contact with, however the surface is orientated. For example in a jug of water, the pressure the water exerts on the bottom of the jug is the same as the pressure it exerts on the sides, at the bottom. [A stationary liquid behaves rather like a pile of slippery spheres. Imagine putting them in a jug. The pull of gravity on the spheres  makes them push on the sides as well as the bottom, as the pile tends to collapse.] The sides of your iron rod aren't exerting a pressure on anything!
A: NO you can't because this formula only applies in liquid pressure.
Regrets 
