rumus matematika

When there are no forces like wind or uplift from
bottom motions of the ocean, the surface of the water
will be flat. (Here and in the following we neglect the
curvature of the earth.) If we then disturb this flat
surface, the surface will not remain in that static
position. Indeed, everyday experience learns that the
disturbance will start to flow away, to spread out. We
can imagine this as if the water consists of many small
water particles, that are densely packed, and which
can move between each other without friction (different
from sand, which can stay static in certain forms). The
disturbance will cause that particles that are higher with
respect to their neighbours have larger potential energy
and will force its lower neighbours to move. However,
since water is (practically speaking) incompressible,
they can only move by pushing their neighbours. And
so on. The main lesson to be learned form this is the
essential role of the (presence of) gravitation, and the
fact that motion of the surface does not correspond to a
similar motion of the water particles. (Compare with a
row of people standing in line, who successively push
their neighbour in front of them: the ‘push’ will travel
through the row, but the people stay at their place.)
That is why a gull at sea will be lifted up and down with
the waves, without noticeable change in position, just
as a ship that meets a tsunami. This exchange of
momentum takes place almost without friction, which is
why the motion will not die out (very different from the
flow of very viscous syrup): the energy of the total
water body, put in by the bottom motion, will practically
speaking remain constant.