# Pressure in Fluids Exe-4A Long Answer Physics Class-9 ICSE Selina Publishers

Pressure in Fluids and Atmospheric Pressure Exe-4A Pressure in Fluids and it’s Transmission Long Answer Type for Class-9 ICSE Concise Physics. There is the solutions of Long 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 and it’s Transmission Exe-4A Long 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 – 4A Pressure in Fluids and it’s Transmission Topics Solution of Exe-4(A) Long Answer Type Academic Session 2023-2024

#### Exe-4A Pressure in Fluids and it’s Transmission Long Answer Type

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

Page 103

#### Answer:

Take a can or large plastic bottle filled with water. Place it on a horizontal surface. Make a series of holes in the wall of the vessel anywhere below the free surface of the liquid. The water spurts out through each hole. This shows that the liquid exerts pressure at each point on the wall of the bottle.

Liquid exerts pressure at all points in all directions

#### Answer:

Consider a vessel containing a liquid of density. Let the liquid be stationary. In order to calculate pressure at a depth, consider a horizontal circular surface PQ of area A at a depth h below the free surface XY of the liquid. The pressure on the surface PQ will be due to the thrust of the liquid contained in cylinder PQRS of height h with PQ as its base and top face RS lying on the frees surface XY of the liquid.

Total thrust exerted on the surface PQ

= Weight of the liquid column PQRS

and = Volume of liquid column PQRS x density x g

= (Area of base PQ x height) x density x g

hence = (A x h) x  x g

This thrust is exerted on the surface PQ of area A. Therefore, pressure is given as shown below.

P = Thrust on surface / Area of surface

P = Ahg / A = hg

Thus, Pressure = depth x density of liquid x acceleration due to gravity

#### Answer:

The principle of a hydraulic machine is that a small force applied on a smaller piston is transmitted to produce a large force on the bigger piston.

Hydraulic press and hydraulic brakes work on this principle.

(Pressure in Fluids and Atmospheric Pressure Exe-4A Long Class-9 ICSE)

#### Question 4. The diagram below in Fig. 4.12 shows a device which makes the use of the principle of transmission of pressure.

(i) Name the parts labelled by the letters X and Y.

(ii) Describe what happens to the valves A and B and to the quantity of water in the two cylinders when the lever arm is moved down

(iii) Give reasons for what happens to the valves A and B

(iv) What happens when the release valve is opened?

(v) What happens to the valve B in cylinder P when the lever arm is moved up?

(vi) Give a reason for your answer in part (v).

(vii) State one use of the above device.

#### Answer:

(i) X : Press Plunger; Y: Pump Plunger

(ii) When the lever is moved down, valve B closes and valve A opens, so the water from cylinder P is forced into the cylinder Q.

(iii) Valve B closes due to an increase in pressure in cylinder P. This pressure is transmitted to the connecting pipe and when the pressure in connecting pipe becomes greater than the pressure in the cylinder Q, valve A opens up.

(iv) When the release valve is opened, the ram (or press) plunger Q gets lowered and water of the cylinder Q runs out in the reservoir.

#### Answer:

Working: When handle H of the lever is pressed down by applying an effort, the valve V opens because of increase in pressure in cylinder P. The liquid runs out from the cylinder P to the cylinder Q. As a result, the piston B rises up and it raises the car placed on the platform. When the car reaches the desired height, the handle H of the lever is no longer pressed. The valve V gets closed (since the pressure on the either side of the valve becomes same) so that the liquid may not run back from the cylinder Q to cylinder P.

#### Answer:

Working: When the pressure on the pedals is releases , the liquids runs back from the wheel cylinder Q to the master cylinder P and the spring pulls the break shoes to their original position and compels the pistons  to retune back  the wheel cylinder Q. Hence, breaks are release.

—  : End of Pressure in Fluids and it’s Transmission Exe-4A Long Answer Type  Solutions :–

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