Question

Which of the following are correct statements?
(1) 760 torr is equal to 1 atmosphere
(2) ${10^6}dynes/c{m^2}$ is called 1 Bar
(3) ${10^5}Newtons/{m^2}$ is Pascal
(4) 1 atmosphere is $1.013x{10^5}dynes/{m^2}$
A. 1,3
B. 1,2
C. 1,4
D. 3,4

Answer 1

Hint: All the options are units of pressure. The SI unit of pressure is pascal.Pressure is usually expressed in units of force per unit of surface area ($P = \dfrac{F}{A}$ ). One pascal is one Newton per square metre of force applied perpendicularly on a surface.

Complete answer:
The torr is an absolute pressure unit defined as exactly $\dfrac{1}{{760}}$ of a standard atmosphere. Thus, one torr equals exactly $\dfrac{{\;101325}}{{760}}$ pascals \[ = {\text{ }}133.32\] pascals. It is a pressure unit corresponding to 1 mm of mercury in a barometer.Atm and torr are related by the equation \[1\,atm = 760\,torr\].

A bar is equivalent to 100 kpa. $dynes/c{m^2}$ is a CGS unit and ${10^6}\,dynes/c{m^2}$is equal to 1 Bar. The pascal is a SI-derived pressure unit that is used to calculate internal pressure, stress, Young's modulus, and ultimate tensile strength and $1\,pascal = 1\,N/{m^2}$. Atm is another unit used to measure pressure and $1\,atm = 1.013 \times {10^{10}}\,dynes/{m^2}$.

Note: The pressure at different points on the earth is different. Points that are at a height experience less pressure, for instance, a person standing on the top of the Himalayas will experience less pressure exerted by the atmosphere than a person standing near to a sea. This is because as moving upwards the volume of air present in the atmosphere decreases and less pressure is exerted.