Sat27November0556PM 16

Absolute pressure can be measured using a mercury barometer. Blood pressure can be measured using a mercury manometer. The units used to measure pressure are the SI units of length (mm).

Why is pressure measured in mmHg?

(Please select 1 option)

Pressure is directly proportional to the density of mercury

Pressure is directly proportional to the weight of the mercury column

Pressure is directly proportional to the force exerted by the mercury column

Pressure is directly proportional to length of the mercury column and is the only constant

Pressure is directly proportional to length of the mercury column and is variable Correct

Explanation

Absolute pressure can be measured using a mercury barometer. The barometer is a glass tube with one closed end. The open end is placed into an open vessel containing mercury. Atmospheric pressure is exerted onto the surface of the mercury in the container pushing the mercury into the tube. The distance between the meniscus in the tube and the mercury surface is absolute pressure.

Pressure is force (F) per unit area (A). The units of force are newtons (N).

Pressure = F/A = N/m2 = N/A

F = mass of mercury column × acceleration due to gravity

Mass of mercury = area (A) × density () × length (L)

Pressure = ((A × × L) × 9.8 m/s2)/A

Pressure = × L x 9.8

Pressure is proportional to L

In the above equation, area (A) as numerator and denominator cancel out. The constants are density and the value of acceleration due to gravity.

Length is directly proportional to the exerted pressure.

Answer Statistics

1

6%

2

6%

3

23%

4

24%

5

43%

Times answered: 234