The speed has nothing to do with calculating pressure. You need to know the mass, acceleration, and area. Furthermore, while pressure itself is a scalar, for non-simple geometries you need to know the vectors of the acceleration and area.

Most people will tell you that pressure is force divided by the area. This is true, but is making an important assumption--the force is normal to unit area.

If you had a square of 1 m^2 and exerted a force of 10 N over its entire area, what is the pressure? The answer is we can not determine from the information provided. If the force is normal to the square then the pressure is 10N / 1m^2 = 10 N/m^2. If the force is inclined at a 45 degree angle then the pressure is 10N*cos(pi/4) / 1 m^2 = 10sqrt(2)/2 N/m^2.

Things get even more complicated if the force is not evenly distributed in which case you'll be doing some integration.