Question

A barometer is carried from the 1st floor to the 20th floor of a building. Why does the reading on the barometer fall?
A. Air pressure has increased
B. Gravity has decreased
C. Temperature has increased
D. There is less air above barometer

Answer 1

Hint: Check the use of the barometer. Use the relation between the air pressure and the quantities such as altitude, gravity and temperature.

Complete step by step answer:
A barometer is an instrument used to measure the air pressure.

If the barometer is carried from the 1st floor to the 20th floor of a building, the altitude of the atmosphere from the surface of the Earth increases.

The air pressure at the higher altitude decreases and does not increase.

Hence, the option A is incorrect.

If the barometer is carried from the 1st floor to the 20th floor of a building, the altitude of the atmosphere from the surface of the Earth increases.

But there is not a huge effect of change in gravity on the change in air pressure. The effect is very small.

Therefore, the increase in height affects the reading of the barometer but is very small.

Hence, option B is incorrect.

The layer of the atmosphere nearest to the Earth is the troposphere.

In the troposphere, the temperature of the atmosphere decreases with the altitude from the surface of the Earth.

Therefore, if the barometer is carried from the 1st floor to the 20th floor of a building, the temperature decreases and not increases.

Hence, the option C is incorrect.

The air pressure decreases with the altitude.

Therefore, if the barometer is carried from the 1st floor to the 20th floor of a building, the reading of the barometer falls due to decrease in the air pressure.
Hence, the correct option is D.

So, the correct answer is “Option D”.

Note:
The air pressure reduces with height due to the effect of gravity but the change is very small so can be neglected.
The reading of the barometer falls due to decrease in the air pressure.