(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 50lg man jumps off a bridge 80m high. He lands in choppy salt water feet first. Each foot has an area of 75cm^2. The goal is to find out

a) What is the force sustained by the human body while hitting then decelerating in the water.

b) depth of penitration

Because this is to check the safety of the jump, ie safe, harmful, or deadly, we can simplify it by ignoring the temperature of the water and air.

known figures.

Salt water = 1.027 g/cm^3

bridge = 80m

total penetration area = 150cm^2

weight of man = 50kg

2. Relevant equations

from the bridge to the water in time

9.8m*s^2 = h

force in a fluid

f= 1/2p*v^2*c*a

because I did not know what the drag coefficient of a human is (a flailing human) I ignored it, and it is unitless.

3. The attempt at a solution

I did not know how to calculate the velocity so I calculated the speed

9.8m*s^2=h

9.8m*s^2=80m

s^2=8.15

s=2.85

I read that at 3 seconds an object has 29.2m/s so I guessed (not very scientific I know) and said 2.85 would be 28m/s

f= 1/2p*v^2*c*a

we nix the c

f=1/2*1.027g/cm^3*2800cm/s^2*150cm^2

f=6*10^8 g*cm^4*s^2/cm^3

f=6*10^8g*cm*s^2

thats ergs right?

Anyway, this is a rough figure but ok for my purposes. I do not know what do to with this figure not though as I want to calculate the amount of force sustained on the body when it hits and as it decelerates as well as how far down it can go.

I have this other equation

Vf^2 = Vo^2 + 2*a*y

but I do not really know what to do with it.

this is not for any scholastic or commercial project (I am a high school drop-out). Rather there is a bridge near me (the sunshine skyway) which is famous for people jumping off it to commit suicide. I am arguing that they survive the fall and then drown.

Thanks for any help given.

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# Homework Help: Force of impact on a human body falling into water

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