[Q] Splashes

[paigetheoracle]

When I throw stones into a body of water I notice sometimes they make a large splash with little sound and sometimes it's a small splash with a loud plop - why is this?

[freeztar]

It has to do with stone geometry, stone mass, velocity, and angle of entry. Throwing a spherical stone nearly straight up in the air should produce a "plop" when it hits the water. If you watch the point of impact, you will notice a momentary crater in the water. As you decrease the angle from 90 degrees, the waves are much more uneven and the sound is not only more directional (in opposite direction of force) but also more irregular/interactive (providing opportunity for standing waves).

 

That's my best guess based on what I know and have experienced. Though, I've thrown big rocks at nearly 45 degrees and experienced a big "plop", so perhaps I'm completely wrong on this.

[paigetheoracle]

I wondered if it was implosion/ explosion differences, sort of like you were saying but the difference between a belly flop and a proper dive (smallest point piercing the water and displacing it vertically upwards versus shock waves dispersed sideways or when you plunge your hand, fingers straight, into a liquid as opposed to slapping the palm of your hand straight onto the surface).

[freeztar]

I see what you are saying, but I don't think it can correctly be called an explosion and/or implosion event. I think a better term is displacement (surface tension should also be considered). I'm not versed in the physics of hydrodynamics though, so it would be nice if someone chimed in with a more appropriate explanation (potentially including equations).