obtain the magnitude of the force that the screw thread exerts on the cap in order to keep it on the bottle?

Question

A glass bottle of soda is sealed with a screw cap. The absolute pressure of the carbon dioxide inside the bottle is 1.65 105 Pa. Assuming that the top and bottom surfaces of the cap each have an area of 4.25 10-4 m2, obtain the magnitude of the force that the screw thread exerts on the cap in order to keep it on the bottle. The air pressure outside the bottle is one atmosphere.
_____N

Answer 1

1 Pa = 1 n/m^2
Atmospheric pressure = 101,325 Pa

The net pressure of the gas inside the bottle is the absolute pressure minus atmospheric pressure,
165,105 - 101,325 = 63,780 Pa

The force on the cap is the net pressure times the area
63,780 * 4.25x10^-4 = 27.11 N