Because the gas pressure decreases and the volume increases when the glass tube rotates to the nozzle downward direction, and the length of the glass tube is limited, it is necessary to judge whether the mercury in the glass tube flows out when the glass tube rotates to the nozzle downward direction.

The right solution:

First, judge the downward (lowest point) of the glass tube nozzle. Assuming that mercury does not flow out when the glass tube nozzle is vertically downward,

According to Boyle's law: P 1V 1=P2V2.

get:(75+ 15)×50s =(75- 15)×L2s？ L2 = 75cm cm

∫75cm+ 15cm = 90cm < 100cm，

Mercury will not flow out when the glass tube passes through the lowest point,

Is it somewhere else? Mercury won't flow out?

Suppose that the length of the air column is L after the glass tube rotates 240. According to Boyle's law, P 1V 1=P3V3.

Get: (75+ 15) × 50s = (75？ 152)×lS

Solution: l=66.7cm

Answer: The above analysis process is incomplete, and the complete connection is as above.