Why is it that when you hit water falling from a great height it's like hitting cement?

Question

I mean, it must be true, judging by what a belly flop off of a high dive feels like.

Answer 1

The molecules are attracted to each other and they don't have enough time to move out of the way for you to hit them. They create surface tension which can only be penetrated at certain speeds.

Play with some cornstarch water (1:2 recipe) to see what I'm talking about.

http://www.youtube.com/watch?v=f2XQ97XHjVw

Answer 2

The relative surface tension of a substance is affected by the force exerted upon it. In the case of water, when you jump into a pool from 1m at a low speed, it's "sploosh"; when you hit it from the cockpit of a cigarette boat at 150mph, it's "schk-schk-schk-ow-(expletives deleted)!" When falling from a great height, you become an instrument of force (= mass (you) x acceleration (gravity)), and as such, an instrument of the acceleration you gain as gravity acts upon you until you hit another object (the water).

At that point, Newton steps in (First and Third Laws of Motion, specifically). The water, as a liquid, is a somewhat loose conglomeration of molecules (energy dissipators), which is made even looser at your impact point; fewer "pillows" to cushion the force means you feel more of it that the water would, therefore the water feels harder.

Answer 3

Most lose consciousness before they hit. It's hard to get a breathe so blood pressure would drop considerably. I would say it is possible if the height was great enough, like from a plane. The pressure changes could wreck havock with you.

Answer 4

Because whoever hits the water from that height is rapidly displacing the water around them creating high surface tension on the water.

Answer 5

okay force being produced by speed makes the impact more severe from heights if you were to run into water force is not the same but drive a moterbike then force is increased so speed of impact makes a lot of difference the higher you go the more speed you gather and the more impact restance when you hit. not the same with cement of course because there is more resistance so you can't fall as far.

Answer 6

Water is heavy, and the higher you fall from, the higher will be your final velocity when you hit the surface. Moreover, water does have surface tension and viscosity so that the impulse of the collision is very high: Impulse= loss of momentum divided by time of the loss process.

Answer 7

Because water is non-compressible. It can be displaced but at that speed it can't get out of the way fast enough. On impact a lot of your kinetic energy is reflected off the water and back into your body. The bigger the surface area contacting the water on impact the more energy gets reflected back.

Answer 8

Water is heavy. That is, it is massive. It takes a lot of energy to displace it. When you hit the water at high speed, there's no time for the water to move out of the way, so it stays put.

And you go splat.

Answer 9

Ouch!!!!

I don't know but I feel for you, now and then. Just the memory of that must hurt.

Hypothesis:
Having done that before, I think our body is like a blanket made of dead weight and when it hits water, we are more like the cement hitting water. That is, before the pain hits us!

Answer 10

The velocity off the moving body is too great to deal with the surface tension of water, thus the "slamming" effect