1 P1=P0,V1=L0S=30SP2=P0+Ph,V2=L1S=25SP1V1=P2V2,所以，P1=75cmHg2 管足够长，水银不溢出 P3=P0-Ph,V3=?P1V1=P3V3,V3=37.5SL0=37.5cm
