Question

The diagram below shows a simple mercury barometer. The mercury level is at a height $h$ when the atmospheric pressure is ${10}^5$ Pa.

What is the pressure at P?

• A. 40,000 Pa
• B. 60,000 Pa
• C. 1,00,000 Pa
• D. 14,00,000 Pa

Answer 1

The correct option is A 40,000 Pa

In a barometer, atmospheric pressure is directly proportional to the height of the mercury level.
Now, height $h$ corresponds to the pressure of 1,00,000 Pa.
So height 0.4 h will correspond to the pressure of 0.4 $\times$ 1,00,000 = 40,000 Pa.
Hence, pressure at P is 40,000 Pa.