# Falling objects

1. Jul 23, 2004

### JBP

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 [Broken]) but can't figure it out - Maybe because my grades back in high-school were terrible :uhh:

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)

Last edited by a moderator: May 1, 2017
2. Jul 24, 2004

### pmb_phy

You weren't clear as to what you were asking. I assume that you're asking what force a rope would exert on a person when the person, who has the rope tied around his waist falls and is prevented from falling all the way to the ground by the rope. That force is F = dp/dt where p is the momentum of the person who is falling and dt is the time inteval during which the person's momenum changes by the amount dp. I also don't know what you mean by "Dynamics of rope (in percent @ 80kg)". you need to know the properties of the rope such as Young's modulus for the rope.

Pete

Last edited by a moderator: May 1, 2017
3. Jul 26, 2004

### JBP

Hi Pete,

When I look at Your answer I can see that what I'm missing is the Young's modulus for the rope.

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 don´t 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. Jul 27, 2004

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

5. Jul 28, 2004