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Old Mar 29th 2018, 06:51 AM   #1
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Calculating "g - force" acting on an Human Body

Dear friends,

I want to know the total g-force acting on an Human Body while accelerating.

Code:
Weight of the Human Body = 70 Kg;
Initial Velocity (Vi) = 0;
Final Velocity (Vf) = 22.22 m/s;
Start Time (ti) = 0 sec;
Final Time (tf) = 1 sec;

delta V = Vf-Vi = 22.22 m/s - 0 = 22.22 m/s
delta t = tf - ti = 1 s - 0 = 1 sec

acceleration (a) = delta V/delta t
                       = (22.22 m/s) / (1 s) = 22.22 m/s2

So, acceleration of the Body = 22.22 m/s2

F = m x a
F = 70 Kg x 22.22 m/s2 = 1555.4 Kg-m/s2 or 1555.4 N

G of Human Body = 70 Kg x 9.81 m/s2 = 686.7 Kg-m/s2 = 686.7 N = 1g
So,
g force acting on the Body at 22.22 m/s2 = 1555.4 N / 686.7 N = 2.265 g

Answer : 2.265g
Is this correct method to calculate the "g- force"? Else,share your idea.

thanks to you all,
pmk

Last edited by SpeedEC; Mar 29th 2018 at 07:10 AM.
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Old Mar 29th 2018, 10:25 AM   #2
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Yes, But...

You have ended up at the correct answer,
but you have gone down a side road, around the block, and back.

Once you have the acceleration of the body at 22.22m/s/s
you can go directly to:
22.22 / 9.81 = 2.265

1g=9.81
how many times larger is 22.22?
22.22 = 2.265 * 9.81

All the messing around with the mass and the force is not necessary.

If you write out the equations you used:
(70*22.2) / (70*9.81)

the "70" at the top and bottom of the division cancels
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Old Mar 29th 2018, 11:03 AM   #3
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Thank you woody for the reply.

Direction of g-force - Horizontal - Chest to Back - Eyeball-in direction;
Safety - with proper cushion provided around the human body;
Impact Distribution - uniform distribution throughout the body;
Acceleration - 22.22 m/s2
Duration = 1 second

After 1 second, body acceleration will be 0 and maintain the uniform velocity of 80 KMPH for few seconds, say around 15 seconds.

I like to know that can the human body withstand against the 2.265g?

thanks,
pmk
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Old Mar 29th 2018, 05:46 PM   #4
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2 to 3g should be fine for a healthy person,
no heart conditions in particular!
There are fairground rides that reach that level.

Fighter Pilots can withstand up to 9g for short periods.
The limiting problem is (usually) the heart being unable to pump sufficient blood to the brain.
Moving the rib-cage to fill the lungs with oxygen can also become an issue.
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Old Mar 30th 2018, 11:43 AM   #5
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Thank you Woody.

pmk
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