The density of the medium through which it is travelling: for example, about 343m/s in air; almost 1500m/s in sea-water.
fast moving
fast
They are generally slow.
slow
Fast moving stream
fast. not that fast but fast.
fast
fast
How fast molecules are moving. If they are moving fast its hot, but if they are moving slow it is cold
Fast moving water will erode faster because it is more powerful than slow moving water.
Normally, they are slow moving snakes.
Friction