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Alright, heres the deal: I weight 68 kilograms( should be about 138 pounds), i'm 1.81 tall if thats neccessery. Anyways, how deep(water ofc) would i go if jump off from a platform. I hope u get what i mean. Platform is 7,5 meters high from water.

pie

So u want jump from platform and its 7.5 meters high?I think its more then enough to jump,xD!

I think he wants to jump from the platform and make sure that once he goes into the pool or whatever, he doesn't break his legs because he goes too fast too deep.

I've jumped from a 5 meter cliff myself into water that was about 5 meters deep and I only went in 2 meters.

I think you need like 4 meters to be totally safe. I'm 64 kg btw.

Not enough information is given to calculate the result.

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ROFL xD

Alright actually i wanna jump from bridge, which is 7.5 meters from water, and i dont know exactly the surface, i know that river shouldnt be over 5 m deep, there are also boats and bigger boats crossing the river,so it should be deep enough. I know its crazy stunt but i really wanna do that.

Only 1 way to find out..

well one time i jumped from a boat and i got really deep in the sea ,luckly i went up fast ,my glasses were full of water and couldn't see anything ,anyway it depends on the way u jump ,if i want to jump and touch the floor then come up i can do it ,if i don't ,i don't

just jump take note later

This is physic, not math...
If today is 3 years ago, i could help u

Yup. You would need the speed your hitting the water at, and the density of the water (Pretty sure)...

OT: Just jump and find out XD

Don't know what your education level is but you can get a nice estimate by doing the following (all of which is around middle school level so I know you'll be able to understand when you google it):
1. Calculate gravitational potential energy at the top of 7.5 meters.
2. Calculate velocity based on height and gravitational accerlation.
3. Calculate kinetic energy at the base of the jump. Forget dissapation by air as it's much too short of a jump to matter.
4. Google energy trasnfer rate for water for a given kinetic energy from above.
5. Subtract it and calculate the kinetic energy left over.
6. Google friction coefficient for water.
7. Multiply water's friction coefficient into energy dissapated to find out how much energy you have left.
8. Solve for velocity and plug it in to a height equation with ground level being the top stopping at 2 decimal places since anything more specific is useless.

I believe there's a much more complicated way to do this but I would not know what it is without looking it up. Unfortuinately it's 5:00 though, so I'm leaving, gl.

ok u can do that or just jump xD

7.5 m high
acceleration is 9.81 m/s²
distance = 0.5 a t ²

lol not wanting to calculater it all
but i can only calculate the speed you hit the water with
but this is without air fraction

im pretty sure it depends on your u dive, if u do a belly flop its definitely going to be far less than if u do a perfect dive

also u have to take account of how much air ur lung can take, if u have a lung full of air its going to be different if your lung is almost empty

etc...

Your right... Toss in an object with the same wight and shape like you, with an air filled 4l bag inside.

It has too many factors. How fast you're going, wind, body position, body movement, how you're entering, etc.

Just disregard those other factors and follow the steps SM typed. This is physics. Assume there is no wind, disregard body position, and air resistance.

Ever skip a rock on a lake?
Disregard body position? Okay, sure, right.

Body position is more important than body weight - question: Disregarding air/wind resistance, what falls faster 1 pound of feathers or 1 pound of lead?

crazyskwrls has the right of it. Distance from sea level, weather factors (is it a hot day), windage, water density (salt water or fresh?) and other factors (like surface tension, is it raining?) will all have a play but when it comes down to the impact and penetration it will rise or fall on how much of your body surface smacks the water. With a feet first high dive, the other factor that will limit the depth is your body's attitude after you penetrate the surface - think about the letter "J" <----- that's the path you want to have the moment after penetration.

Going head first? Don't go alone.
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I used to dive alot but never from any height above 40'. The way we were taught for shallow head first dive was for lifeguard style rescue (completely different). It's like trying to bellyflop and stretching out all the way at first then, just prior to impact, tuck the belly up and try to form a semi-circle with elbows, forearms and legs hitting first, then belly thrust and spread immediately after impact. That was a completely different form but watch the video, you'll get the idea. I wouldn't even think about high dive into shallow, but if you are not able to surface dive to the bottom without stopping to clear your ears it's probably deep enough. On the vid above - check it out from 1:23 to 1:26, looks like that is the approximate distance you're thinking about, right? I'd still advise against it; the bottom surface is irregular, and if unknown, caution should prevail. What if there were a log down there? Or worse, a piranha that could bite your pee-pee off

~Granps

basically you shouldntgo deeper then 5m,ive jumped from 7m high platform to 6m deep water,my legs didnt touched the bottom,and if its deeper then 5m then you prolly just touch gently the bottom with your legs:)

So much trouble about one jump, just jump. From that height 2 meteres of waters is more then enough.
I have some crazu friend that jumped from bridge about 20 meters and water wasnt to deep either, altough he is insane .

Granps you know what I mean. I thought we were assuming he was going in feet first which is why we can disregard the position of his body as I thought it would be understood. How did I infer this? Well he want to know how deep he will go and he doesn't want to get hurt. A belly Flop won't go deep, head first and he might crack his skull. In Physics when doing experiments you're usually told to disregard air-resistance and wind for simplicity. Don't try to complicate things, remove unnecessary variables so you can get a round-about number.

Here we go. Name A the point of leaving the bridge; B the point of touching the water.

Energy in A = Energy in B (by the energy conservation law)

EcA + EpA = EcB + EpB (Ec = kinetic energy; Ep = potential energy)

Obviously, EcA = 0, because EcA = m * v ^ 2 / 2, and the velocity is 0 in that point.

Also, EpB = 0, because EpB = m * g * h, and the relative height, in this case, is 0.

We're left with:

EpA = EcB, hence m * g * h = m * v ^ 2 / 2, where h = height, v = velocity, m = mass, g = gravitational acceleration.

Conclusively v = sqrt(2 * g * h). Computed: v = 12,1243 m / s

EDIT: Kinetic energy upon touching the water:
EcB = m * v^2 / 2 = 68 * 147 / 2 = 34 * 147 = 4998 J.

I don't know how to calculate SM-Count's next steps, the first three is all I could do. I lack the theoretical base regarding friction and energy loss equations.

Body position is important.
for example:
http://www.nothingtoxic.com/media/12152 ... each_House

i lack physics rules ,i really forgot physics after the exam

just jump, if you break any legs well then you know you'll never do it again.. you learn about your mistakes

I studied physics for like 8 year:)
All i can say is: experiments, experience, practice.
Thats all.
First from low heights and slowly go for higher jumps.
Practice and experience, not just
BOOOYAAAA!!!.... (ckrack) -> dead

Easy enough. Don't jump or a piranha will bite your pee-pee off, but I thought I covered that.

ps/edit:
if you do it, do it in style.
listen to this music before.
http://www.youtube.com/watch?v=xY-oili63QQ
helps a lot:D

arghnnooo wrong button T_T