# Pressure in Fluids Exe-4B Numericals Answer Physics Class-9 ICSE Selina Publishers

Pressure in Fluids and Atmospheric Pressure Exe-4B Atmospheric Pressure and it’s Measurement Numericals Answer Type for Class-9 ICSE Concise Physics. There is the solutions of Numericals Answer type Questions of your latest textbook which is applicable in 2023-24 academic sessionVisit official Website CISCE for detail information about ICSE Board Class-9.

## Pressure in Fluids Exe-4B Atmospheric Pressure and it’s Measurement Numericals Answer

(ICSE Class – 9 Physics Concise Selina Publishers)

 Board ICSE Class 9th Subject Physics Writer / Publication Concise selina Publishers Chapter-4 Pressure in Fluids and Atmospheric Pressure Exe – 4B Atmospheric Pressure and it’s Measurement Topics Solution of Exe-4(B) Numericals Answer Type Academic Session 2023-2024

#### Exe-4B Atmospheric Pressure and it’s Measurement Numericals Answer Type

Ch-4 Pressure in Fluids and Atmospheric Pressure Physics Class-9 ICSE Concise

Page 113

#### Question 1. Convert 1 mm of Hg into pascal. Take density of Hg = 13.6 x 103 kg m-3 and g = 9.8 m s-2 .

We know that, the pressure is given by the formula,

δP = hρg

Putting the given values in above equation, we get,

δP = 0.001 x 13.6 x 1000 x 9.8

δP = 133.28 Pa

Therefore, 1 mm of Hg is equal to 133.28 pascals.

#### Question 2. At a given place, a mercury barometer records a pressure of 0.70 m of Hg. What would be the height of water column if mercury in barometer is replaced by water? Take density of mercury to be = 13.6 x 103

Relative Density of Hg = 1.36 = kgm 13.6 × 103 kgm-3

Acceleration due to gravity , g = 9.8  msms-2

Height of mercury column = 0.70 m

∴ Pressure , P = hρg

or , P = (0.7)(1.36 × 103)(9.8) pascal

or , P = 93.3 × 103 Pa

Let h be the height of water column

Then , P = h (density of water) g

or , 93.3× 103 = h × 103 ×9.8

or , h = 9.52 m

#### Question 3. At sea level, the atmospheric pressure is 76 cm of Hg. If air pressure falls by 10 mm of Hg per 120m of ascent, what is the height of a hill where the barometer reads 70 cm Hg. State the assumption made by you.

Atmospheric pressure , P = 76 cm Hg

Rate at which pressure falls = 10 mm of Hg per 120 m of ascent = 1 cm of Hg per 120 m of ascent

Let h be the height of the hill.

Pressure at hill , P’ = 70 cm Hg

Total fall in pressure = P – P’ = (76 – 70) cm Hg = 6 cm Hg

Now , fall in pressure is 1 cm Hg for every 120 m increase in height

Thus , if the fall in pressure is 6 cm Hg , increase in height shall be (6 × 120)m = 720 m

∴ Height of the hill = 720 m

Assumption: Atmospheric pressure falls linearly with ascent.

(Pressure in Fluids and Atmospheric Pressure Exe-4B Numericals Class-9 ICSE)

#### Question 4. At sea level, the atmospheric pressure is 1.04 x 105 Pa. Assuming g = 10 m s-2 and density of air to be uniform and equal to 1.3 kg m-3, find the height of the atmosphere.

Pressure = hdg
h = Pressure / (dg)
= (1.04 × 105 Pa) / (1.3 kg/m³ × 10 m/s²)
= 8000 m
= 8 kilometers
Height of the atmosphere is 8 kilometers