Realtion between pressure and area ?

[ameer]

pressure p = force F/ area.pressure decrease with increase in area and increase with decrease in area. now in the nozzle, as area of nozzle decrease pressure reduce and velocity increase. Why?

[brhm]

Velocity increases because you transfer same volume from a smaller area.(q=Velocity*Area).
when you have higher velocities, the flow pattern of the fluid will change and causes pressure drop.

[AfigueredoU]

There is an additional point to think about, is the energy conservation equation, that means, that if the velocity increase (due of area reduction) the pressure must be reduce in order to keep the same energy qantity (less lost due to friction) see bernoulli principles.