PHYSICS PRESENTATION

Force & Pressure

UNDERSTANDING

PRESSURE IN LIQUID

PRESSURE IN LIQUID

Depth, h Acceleration due to gravity, g

Density of the Liquid, p

Application

Example of Idea

When a scuba-diver descends deeper in the sea, the

body and the ears of the scuba-diver feel

uncomfortable .This is due to the pressure of the liquid

(water) acting on the body of the scuba-diver. A liquid

exerts pressure of an area under the surface of a liquid

. This is because the liquid has weight.

Characteristics of Pressure

in a Liquid

The pressure at a point in a

liquid, at a particular depth,

actsequally in all

directions

The pressure does not depend on the

shape or size (surface area)

The pressure in a liquid is

affected by the force of gravity

Factors That Affect The

Pressure in a Liquid

Depth of the Liquid

The pressure in a liquid is affected by the force of gravity. Density of

the Liquid

The pressure in a liquid increased with depth.

Strength of

Gravity

Deriving Formula for Pressure in

Liquid

Depth, hDensity, p

Base Area, A

• Volume of liquid V = Ah• Mass of liquid pV = Ah• Weight of liquid mg = pAhg• Force on base pAhg • Pressure F/A = pAhg/A = pgh

Hence, pressure in liquid = pgh

Application of Pressure in Liquids

Dam holds water at high altitude. The wall of the dam has to be thicker at the base. This is because it must withstand the increased lateral pressure in depths of the water.

Water is stored in water tank at higher level to supply water at greater pressure.

Submarine is built with thick wall to withstand enormous pressure at greater depth.

A patient receiving intravenous drips of a certain fluid from a bottle. In order for the fluid to flow into the vein, the bottle must be placed at a height above the injection site. The liquid at the higher pressure so it has sufficient pressure to flow into the veins of the patient.

CHECK YOUR PROGRESS

QUESTION 1

An air bubble is at a depth of 3 m below the surface of lake. What is the pressure of water on the air bubble?

(take density of water = 1000 kgm-3 and consider the gravitational accelaration is 10ms-2 )

Solution:

h = 3m g = 10ms-2p = 1000 kgm-3 P = hpg = 3 x 1000 x 10 = 30 000 Nm-2 = 30 Kpa

Calculate the water pressure at the bottom of the dam when the wateris at maximum level.( take density of water is 1000 kg and consider the gravitational acceleration is 10ms-2)

25m

QUESTION 2

Solution:

water pressure at the base of dam =hpg h = 25p = 1000g = 10 P = 25 x 1000 x 10 = 250 000 N m-2

= 250 KPa

Learning Physics is Fun..

Goodbye…

Credits…K.Ilakiya

Sharanee S.ShivaniS.Shaleni

Khairol Anwar