Slideshare about Pressure for grade seven.

1. Physics
Pressure
Sarah Ghandour
Grade 9
2014/2015

2. Outlines
• Define the term “Pressure”.
• Specify the relationship between pressure, force
and area.
• Relate pressure to force and area, using
appropriate examples.
• Come up with the conclusion that pressure in liquid
varies with depth of the same liquid and also with
the liquid density at a given depth.
• Solve problems using the formula P=hg.

3. Pre-requisites:
• Students have learnt:
-Gases and liquids are matter
-What a force is
-That downward force exerted by Earth is called
weight (mg).
-The definition of density of a fluid as mass per unit
volume.

4. What is Pressure?
• Pressure is a push or
force against a surface.
• the weight of the air in
the Earth's atmosphere
(atmospheric pressure)

5. Pressure
Pressure of gases Pressure of fluids
• The measurement of
the weight of the gas
above an object on a
given surface area.
• P = F/S
• The pressure under
water or any liquid
increases with how
deep you are.
• Hydrostatic pressure
• P = D*g*h

6. Pressure
Force/area
Liquid
Acts equally
in all
directions
P*g*h
Pressure
increases
with depth
Depends on
density of
liquid
Does not
depend on the
shape of the
container
Solid
weight/area
Summary

7. Exercise 1
• Fill a glass with water and cover it with a cardboard.
• Turn the cup upside down.
• Would the cardboard drop down?

8. Exercise
• The same solid has two different faces.
• Is the pressure the same if the object was placed on
different faces as shown in the figure below?
• Same pressure
• Different pressure