When you drop a stone into a pool why does it make moving concentric rings which get bigger and fade out?

Answer 1

Kinetic energy and gravity.

Answer 2

The water in the pool is a medium that can propagate waves of various types. One type of wave is a ripple moving in some direction, with some wavelength. Waves that have "small" amplitude and add and subtract to form more complex patterns of waves.

Waves of any particular type will not appear unless they are excited. One type of excitation might be wind blowing across the pond, which might excite parallel ripples propagating in the direction of the wind.

When you drop a stone in the pool, the temporary displacement of water excites certain wave modes and not others. The ones that are excited make the concentric ring pattern. The rings must fade out as they get bigger because you have only put a certain amount of energy into the modes, and as they propagate outward the average amplitude must decrease.

Answer 3

The waves are not the moving of water away from the stone's impact.It is the energy moving away. The larger the stone (kinetic energy), the larger the waves.
As to why they shrink and diminish, the waves grow in circumference (which means the energy has more water to move) and the energy causes they water to oscillate (move ninety degrees opposite to the wave's direction). As this osculation occurs, it causes the water to move against gravity, expending work. As this work, kinetic energy) approaches zero, the ripples stop..

Answer 4

The stone at first causes a wave to form due to displacement of water by the mass of the stone, and, at the same time, displaces water which springs upwards out of the water in the form of droplets which fall back to the water.

The effect is a series of ripples which, in effect are very tiny tidal waves spreading out across the pool.

At the 'epicentre' the waves are at their largest and, as they spread out they lose energy and dissipate.

The larger the stone, the greater the effect.

Answer 5

Those waves are called ripples, they form due to displacement of mass of water which creates a force circularily outwards.

Answer 6

You are giving energy to water, which travels as waves.
Water does not displaces but particles in water ossilate and gradually lose energy.

Answer 7

its something we call "diffraction" =]