The force of water
Unlike gases, liquids such as water cannot be compressed, at least
not noticeably so under everyday conditions. Water under pressure is
really useful for cleaning down walls or the car; rain washes soil and
rocks down rivers and streams; the ocean pounds against the shoreline
creating cliffs and caves, and the whole Earth is shaped by the forces
exerted by water.
Pressure from the household water supply arises because of gravitational
forces. Dams and water storage tanks are higher than the house so that
the stored water has gravitational potential energy. Sometimes pumps
are used to increase pressure where the gravitational potential energy
of the water is not enough to create the pressure required by the user.
Water in action
Surfers make use of the energy of water as they get raised by the surf
wave, then are pushed along the wave front.
Rising and falling of waves can also be used to turn generators that
produce electric power.
Beaches are formed by the force of water driving small pebbles
and sand towards the beach, then dumping it as the kinetic energy of
the water diminishes.
Water to electricity
Gravitational potential energy stored in the water in dams when
released through pipes and allowed to run down hill is converted to
kinetic energy in the form of moving water. When this water hits the
turbine blades in a hydroelectric power station, the kinetic energy
of the fast moving water is converted through the turbine blades and
generator into electrical energy. In this way the pressure on the water
in the dam is converted to usable electrical energy at the bottom of
the hill.
Rivers deposits
A river often starts high up in a mountain or raised terrain with lots
of gravitational potential energy. It flows rapidly to begin with quickly
converting its potential energy to kinetic energy, carrying with it
rocks and debris of all sizes. As the river slows and the kinetic energy
of the river decreases it can no longer move the larger rocks so they
get left behind. As the river reaches the flat lower level plains, smaller
and smaller particles are only able to be moved until, finally, near
the estuary only the finest sand and silt is left. In this way the energy
of water changes the characteristics of the river, eroding the upper
reaches, transporting material and depositing material in the lower
reaches.
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