8. The average pressure exerted on a piston during each power stroke is termed __________.

Mean effective pressure is the average pressure acting on the piston during the power stroke, derived from the indicator diagram. It represents a hypothetical constant pressure that would produce the same work as the actual varying pressure during that stroke. This distinguishes it from indicated horsepower, which is a measure of power, and compression and exhaust pressures, which occur during other phases of the engine cycle.