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Falling objects 
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#1
Jul2304, 05:15 AM

P: 3

Hi there,
I've spent some hours on trying to make a simulator (in Excel) for calculating the forces involved in a climbers fall. I've found the following link (http://toad.stack.nl/~stilgar/calc.php) but can't figure it out  Maybe because my grades back in highschool were terrible Could anyone please help me making the formulas? The following variables will be available:  Lenght of rope (in meters)  Fall factor / Height of fall  Dynamics of rope (in percent @ 80kg)  Weight of climber (in kg) Thanks in advance 


#2
Jul2404, 04:43 AM

P: 2,954

Pete 


#3
Jul2604, 04:01 AM

P: 3

When I look at Your answer I can see that what I'm missing is the Young's modulus for the rope. So lets start with that. I've found this formula: E = (L*F)/(l*A) E: Young's Modulus L: Length of the rope l: Change in lenght F: Force A: Area of the rope I donīt know what units to use, please correct me in this example: L = 100 meters l = 7 meters (dynamics = 7%) F = 784,8 newtons (80 kg x 9.81) A = 314,29 mm^2 (10mm x 10mm x pi) E = 35,67 (100*784,8 / 7*314,29) 


#4
Jul2704, 12:32 PM

P: 699

Falling objects
doesnt the rope act as a spring, it decelerates the faller. Dont you need the ropes spring coefficient?



#5
Jul2804, 03:10 AM

P: 3

I see Your point  do You know how to find/calculate the spring effect? 


#6
Jul2804, 10:49 AM

P: 699

well, you need to know the spring constant (k). This is in N/m. Then you can use the equation E = 1/2kx^2, where k is the spring constant, and x is the amount of strech from the resting possition of the rope. The force exerted on the object being stopped by the rope would be F = kx. You can play around with there equations and find the right constant so the gforce on the person is not too high.



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