HYDROSTATIC FORCE

Hydraulics

Topic 1
Hydrostatics Forces on Surface

Pascal’s
Law

Pascal’s law says that
pressure applied to an
enclosed fluid will be
transmitted without a change
in magnitude to every point
of the fluid and the walls of
the container. The pressure
at any point in the fluid is
equal in all directions.

definition Pascal Law Formula
F = PA
• Where F is the force applied,
• P is the pressure transmitted, and
• A is the cross-sectional area

Hydrostatic pressure ( P = ρgh = ɣh ) The pressure exerted by a fluid at equilibrium at a
given point within the fluid, due to the force of
gravity. Hydrostatic pressure increases in proportion
to depth measured from the surface because of
the increasing weight of fluid exerting downward

force from above

Definition Center of gravity/ center of mass (cg)
The point at which the entire weight of a body may be
considered as concentrated so that if supported at this
point the body would remain in equilibrium in any
position

Center of pressure ( cp)
The point of a surface exposed to external pressure (as of a fluid) at
which a single force must be applied to equal or counterbalance the
pressure forces acting on the whole surface

Hydrostatic
forces



Hydrostatic
force in
vertical
plane
surface

Moment & Geometric of plane surface

Hyrostatic
forces on

plane
surface





Hydrostatic force
on curve surface



Case of Curve Surface

Problem & solution









Solve the problems

Problem 1 Problem 2

Hydrostatic

force on
inclined
surface

Problem & solution

Total hydrostatic force on curved surface

Hydrostatic
forces on
curved
surface

Curve surface

Problem & solution

Problem & solution

Gravity Dam Analysis

• Dams are structure whose purpose is to raise the water level on
the upstream side of river, stream, or other waterway. The rising
water will cause hydrostatic force which will tend the dam to
slide horizontally and overturn about its downstream edge or
toe. The raised water level on the upstream edge or heel will also
cause the water to seep under the dam. The pressure due to this
seepage is commonly called hydrostatic uplift and will reduce
the stability of the dam against sliding and against overturning.

Gravity Dam
Analysis

The weight of gravity dam will
cause a moment opposite to the
overturning moment and the
friction on the base will prevent
the dam from sliding. The dam
may also be prevented from
sliding by keying its base into the
bedrock.

Steps