Question

which unit of pressure is derived from the early barometers used to measure pressure?

• mmhg
• bar
• pa
• atm

Explanation:

Analyze the origin of early barometers

Early barometers, invented by Evangelista Torricelli, used a column of liquid mercury (\(\text{Hg}\)) in a glass tube to measure atmospheric pressure.

Relate the measurement to pressure units

The height of the mercury column, measured in millimeters (\(\text{mm}\)), directly corresponds to the pressure exerted by the atmosphere, giving rise to the unit millimeters of mercury (\(\text{mmHg}\)).

Evaluate the given options

• \(\text{mmHg}\): Directly derived from the height of mercury in early barometers.
• \(\text{bar}\): Metric unit defined as \(10^5\text{ Pa}\), not directly derived from early physical barometers.
• \(\text{Pa}\): SI unit (Pascal) defined as one newton per square meter.
• \(\text{atm}\): Standard atmosphere, defined based on average atmospheric pressure at sea level.

Answer:

• (A) mmHg (Correct answer)
• (B) bar
• (C) Pa
• (D) atm