SCIENCE FORM 2 CHAP 8 (8.2)

CHAPTER 8
FORCE AND MOTION

3

Pressure

 Gas pressure
 Atmospheric pressure
 Liquid pressure

ATMOSPHERIC PRESSURE

MEANING

• Meaning: the pressure exerted by the atmosphere on the
surface of the Earth and all object on the Earth.

• Couse by the weight of air molucules in the atmosphere

PRINCIPLE OF ATMOSPHERIC
PRESSURE

Air will flow from a region of higher air
pressure to a region of lower air pressure.
This movement of air is caused by a force
acting in the direction of higher to lower air
pressure.

PRINCIPLE OF AIRMOSPHERIC
PRESSURE

If a surface lies between two regions of
different air pressures,

a force will act on the surface in the
direction of higher to lower air pressure.

APPLICATION OF THE
PRINCIPLE OF AIR PRESSURE

1-SYRINGE

When the piston is pulled
upwards, the volume of air
in the barrel increases
The air pressure in it is
reduced
The higher outside pressure
forces the water through
the needle into the barrel

ATMOSPHERIC PRESSURE IN
DIFFERENT ALTITUDES

LIQUID PRESSURE

Effect of Depth on liquid pressure

1. An object in a liquid experience pressure.
2. This is because the weight of the liquid acts on the whole
object, exerting pressure on it.
3. This pressure increase as the depth increases.

Aim: to study the effect of depth on pressure in water.

Observation: the size of air bubbles increases as they
move upwards to the surface of the water.

LARGE BUBBLE:
low liquid pressure
volume of gas increase

SMALL BUBBLE:
low liquid pressure
volume of gas increase

Aim: to study the effect of depth on pressure in water.

Observation: Higher hole will shoot out water futher
than lower hole

Effects of depth on liquid
pressure in daily life.

1. The wall of dam
The walls of the dam are built and designed wider at the base to
hold water which has a high pressure at its base.

2.Submarine

The body of the submarine is made of strong material to
withstand high water pressure so that it would not crushed.

3. Water tank

The tap is put at the bottom of tank
 High pressure, so the water flow fastly