Absolute pressure in a gas model
A fictional accumulator worksheet states that a gas occupies 100 cubic inches at an absolute pressure of 1000 pounds per square inch. It is compressed slowly to an absolute pressure of 3000 pounds per square inch while temperature remains constant. The exercise explicitly treats the gas as ideal and supplies absolute values, avoiding an unknown ambient-pressure conversion. A learner adds the pressures and reports 4000 cubic inches; another uses the inverse pressure-volume relationship. The task asks for the final volume and the reason that a different reference would matter. No real accumulator precharge, hydraulic fluid quantity, servicing method or safe disconnection state is supplied. A correct answer keeps the ideal calculation separate from actual maintenance and recognizes that stored pressure can remain hazardous even after a pump is switched off.
1. Calculate the final model gas volume.
Read the worked answer
At constant temperature, P 1 V 1=P 2 V 2. Therefore V 2=1000×100/3000, approximately 33.3 cubic inches. The supplied pressures are explicitly absolute.
2. Why would unqualified gauge readings be insufficient?
Read the worked answer
Gauge readings use an ambient reference. They would need conversion using the relevant ambient pressure before applying this ideal absolute-pressure ratio.