Tag: important points about atmospheric pressure

Questions Related to important points about atmospheric pressure

Water barometer is possible provided barometer tube is _____$m$ long.

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. $1$

  2. $3$

  3. $5$

  4. $11$

Show answer
Correct Option: D
Explanation:

If water would be used in barometer, barometer tube should have the huge height of $10.3m$ Mercury is $13.6$ times more dense than water and a column weight of only $760 mm$ of Hg equals the forces generated by atmospheric pressure, so the tube can be much shorter.

Mercury is more dense. Its relative density is $13.534$ times that of water. So, to measure the atmospheric pressure, which is $760 mm$ of mercury you need a barometer ,with mercury, of length slightly more than $0.76 m$, say one meter to cover the special cases of some higher pressure. If you use water, you have to have the length of barometer of length (or height)  $13.534$ times the length of mercury barometer, which may be more than $11 m$ in length. Further mercury, being a metal has the shining quality which highlight its reading clear. Also mercury, having comparatively lower specific heat and good conductor of heat, could come to the same temperature of the atmosphere more quickly.

Water is not used as a barometric liquid because 

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. it is difficult to have a barometer tube 11 m long.

  2. water vaporises under vacuum conditions.

  3. water sticks to the side of glass tube.

  4. all the above

Show answer
Correct Option: D
Explanation:

Mercury is more dense. Its relative density is $13.534$ times that of water. So, to measure the atmospheric pressure, which is $760 mm$ of mercury you need a barometer ,with mercury, of length slightly more than $0.76 m$, say one meter to cover the special cases of some higher  pressure. If you use water, you have to have the length of barometer of  length (or height)  $13.534$ times the length of mercury barometer, which  may be more than $11 m$ in length. 


Further mercury, being a metal has the shining quality which highlight its reading clear. Also mercury, having comparatively lower specific heat and good conductor of heat, could come to the same temperature of the atmosphere more quickly.

The weight of the column of the mercury in the tube above the surface of the mercury in the cup is balanced by

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. The weight of air column

  2. Friction Force

  3. Viscous Force

  4. Buoyant force

Show answer
Correct Option: A
Explanation:

Answer is A

The weight of mercury column is balanced by air weight and the weight of mercury column is used to calculate the pressure. 

Which of the following scientists invented the mercury barometer?

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. Blaise Pascal

  2. Evangelist Torricelli

  3. James Joule

  4. Robert Brown

Show answer
Correct Option: B
Explanation:

Mercury barometer was invented by scientist Evangelist Torricelli

It is known fact
Therefore option $B$ is correct 

A barometer kept in a stationary elevator reads $76$ cm. If the elevator starts accelerating up the reading will be:

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. Zero

  2. Equal to $76$cm

  3. More than $76$cm

  4. Less than $76$cm

Show answer
Correct Option: C
Explanation:

The movement of elevator up will increase value of g which will result in increase in pressure leading to increase in reading of barometer.

A nurse measures the blood pressure of a seated patient to be $190$ mm of Hg.

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. the blood pressure at the patient's feet is less than $190$ mm of Hg.

  2. the actual pressure is about $0.25$ times the atmospheric pressure.

  3. the blood pressure at the patient's neck is more than $190$ mm of Hg.

  4. the actual pressure is about $1.25$ times the atmospheric pressure.

Show answer
Correct Option: D
Explanation:

${ P } _{ exp }=P _{ 0 }+{ P } _{ Actual }\ 190=76+{ P } _{ Actual }\ { P } _{ Actual }=114mm\quad of\quad Hg\ Factor=\cfrac { { P } _{ Actual } }{ { P } _{ atm } } =\cfrac { 114 }{ 76 } \approx 1.25$

Match the following.

List-I(Measuring Instruments) List-II(Which measure)
A. Anemometer $1$. Motor Power
B. Tachometer $2$. Wind speed
C. Dynamometer $3$. Revolutions per minute
D. Barometer $4$. Atmospheric pressure
$5$. Current from a dynamo
physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. A-$2$, B-$3$, C-$1$, D-$4$

  2. A-$2$, B-$1$, C-$3$, D-$4$

  3. A-$1$, B-$3$, C-$5$, D-$4$

  4. A-$1$, B-$3$, C-$5$, D-$2$

Show answer
Correct Option: A

A barometer kept in a stationary elevator reads 76 cm. If the elevator starts accelerating up, the reading in barometer will be:

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. Zero

  2. Equal to 76 cm

  3. More than 76 cm

  4. Less than 76 cm

Show answer
Correct Option: D
Explanation:

Since the elevator is accelerating up, so, the force will act in the downward direction.

Therefore, the reading in the barometer will be less than 76 cm

The atmospheric pressure and height of barometer column is $10^5 P _a$ and 760mm respectively on the earth surface. If the barometer is taken to moon then column height will be

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. zero

  2. 76 mm

  3. 126.6 mm

  4. 760 mm

Show answer
Correct Option: A
Explanation:

Since there is no atmosphere on moon, no atmospheric pressure will be there and hence corresponding to 0 pressure, height of mercury column will be 0.


Answer is option A.

Fill in blanks. 
Atmosphere pressure _________ with increase in altitude 

physics pressure in liquids and gases common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. increases

  2. decreases

  3. remains same

  4. cannot be determined

Show answer
Correct Option: B
Explanation:

Pressure with Height: pressure decreases with increasing altitude. The pressure at any level in the atmosphere may be interpreted as the total weight of the air above a unit area at any elevation. At higher elevations, there are fewer air molecules above a given surface than a similar surface at lower levels. For example, there are fewer molecules above the 50 km surface that are found above the 12 km surface, which is why the pressure is less at 50 km.

Hence, Atmosphere pressure decrease with an increase in altitude