Insert the 1m long glass tube with one end closed and uniform opening into the mercury groove 25cm deep downward. When the atmospheric pressure is equal to the pressure generated by 75cm high mercury column, the height of mercury column entering the tube is () A.11.6 cm B.13.4 cm C.25 cm D.38.4 cm

Insert the 1m long glass tube with one end closed and uniform opening into the mercury groove 25cm deep downward. When the atmospheric pressure is equal to the pressure generated by 75cm high mercury column, the height of mercury column entering the tube is () A.11.6 cm B.13.4 cm C.25 cm D.38.4 cm

The initial pressure of the gas enclosed in the tube is 75 cmHg and the length is 1 m;
Assuming that the subsequent length of the gas pressure in the tube is shortened by x cm, the final state pressure of the gas is (75+25-x) cmHg and the length is (100-x) cm;
According to Boyle's law, there are: P1V1=P2V2;
That is:75×100=(75+25-x)(100-x)
Solution: x=13.4cm or x=186.6cm (unrealistic, discarded);
That is, the height of the mercury column entering the pipe is about 13.4 cm;
Therefore: B.

As shown in the figure, the U-shaped glass tube with uniform inner diameter is vertically placed, with a cross-sectional area of 5cm^2, the upper end of the right side of the tube is closed, and the upper end of the left side is opened. The piston bolted with thin line inside, regardless of its mass, is sealed with air columns A and B with L=11 in the two pipes respectively, and the body pressure of the upper and lower parts of the piston is 76. At this time, the mercury height difference in the two pipes is 6. Now, the piston is slowly pulled up with the thin line to make the silver surface in the two pipes level, regardless of the temperature change, then: What is the distance the piston moves up? How much tension is required to keep the piston stationary at this position?

(1) Part B gas is taken as the initial state: PB1=76-6=70(cmHg) VB1=11S (cm3) end state: PB2=pVB2=(11+3) S (cm3) According to Boyle's law PB1VB1=PB2VB2PB2=PA2=PB1VB1/VB2=70x11s/14s=55(cmHg) Part A gas is taken as the initial state: pA1=76(cmHg) V...