Thus, in the actuator extension example, the effective cross sectional area of {TAIL ~ the air mass volume exhaust} is increased: in the actuator contraction instance {HEAD ~ the cross sectional area} of the air mass volume exhaust is decreased 
Thus , in the actuator extension example , the effective cross sectional area of { TAIL ~ the air mass volume exhaust } is increased : in the actuator contraction instance { HEAD ~ the cross sectional area } of the air mass volume exhaust is decreased
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH