# Which travels fastest?

1. Jan 13, 2005

### Crumbles

[a] a wave on the surface of the sea?
a wave on the surface of liquid mercury (dense metal)?
[c] a wave on the surface of liquid mercury on the moon?

2. Jan 13, 2005

### ceptimus

I think that denser liquids, and higher gravity both increase a wave's speed (but I'm only guessing). If I'm right, then would be the fastest.

3. Jan 14, 2005

### hemmul

As far as i remember, the rough approximation to the surface-wave-velocity is v~sqrt(g*h), where h is the depth of the "lake".
now, imho "the denser the liquid - the greater the speed" is conserved for surface waves, so is the answer we are looking for...

4. Jan 22, 2005

### Pseudopod

I think for surface waves it is the other way around - less dense=faster. Imagine if the ocean was a light foam. Any sort of surface wave you make would travel very fast. Now, if you imagine a pool of mercury it would be much slower because it has more intertia.

So I think the answer is A) water. But I didn't try to use any math so I could be way off because intuition can be misleading...

5. Jan 25, 2005

### RandallB

Using the intuitive approch imagine the first wave being started from within a box where we insantly remove the bottom and one side.

The light foam like water would have much less potential energy stored to convert into kinentic energy. Being less forceful and moving more slowly on the other light foam like water. While the heavy would move more energy in a smaller wave would likly move faster. Same reasoning for taking B over C for the more force in high G.

(Now watch it turn out to be the same for all!!)