A uniform tube closed at aone end, contains a pellet of mercury 10cm long. When the tube is lept vertically with the closed-end upward, the length of the air column trapped is 20cm. Find the length of the air column trapped when the tube is inverted so that the closed-end goes down. Atmospheric pressure`=75cm of mercury.

Explanation

To solve the problem, we need to analyze the situation using the ideal gas law and the concept of pressure in a closed system. Let's break it down step by step.

### Step 1: Understand the Initial Conditions
Initially, the tube is closed at one end and has a mercury pellet of length 10 cm. The air column trapped in the tube is 20 cm long. The atmospheric pressure is given as 75 cm of mercury (cmHg).

### Step 2: Calculate the Initial Pressure of the Air Column (P1)
When the tube is upright (closed end up), the pressure exerted by the trapped air (P1) can be calculated using the atmospheric pressure and the height of the mercury column:

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