An airtight box, having a lid of area 12 in2, is partially evacuated. Atmospheric pressure is
15 lb/in2. A force of 108 lb is required to pull the lid off the box. The pressure in the box
was:
The atmospheric force on the top of the lid is 12 x 15 = 180 lb. Subtract 108 for the net force oto the top from above. That equals the force due to inside pressure
180 - 108 = P(inside) * 12 in^2
72 lb = P(inside) * 12
P(inside) = 6 lb/in^2
To find the pressure in the box, you can use the formula:
Pressure = Force / Area
In this case, the force required to pull the lid off the box is given as 108 lb, and the area of the lid is 12 in^2.
So, by substituting these values into the formula, we can find the pressure:
Pressure = 108 lb / 12 in^2
Pressure = 9 lb/in^2
Therefore, the pressure in the box was 9 lb/in^2.