KN is this acurate?

[Tony Croft aka hamadryad]

What you may be wanting are a combination of speed distance calculations and force calculations. I did A level physics and maths back in the day and vaguely remember working out stuff like above.

 

v=u+at where v = final velocity u = initial velocity + acelleration x time

 

v= 9.81x3

 

final velocity is 29.43 metres per second

 

s=0.5xat2

therefore the distance fallen is 0.5*9.81*9 = 44m approx 150feet

 

I may come back and calculate the force later. But my brain hurts.

 

good stuff, I think I need to get some evening classes in physics chemistry and math myself, weak on all those!

 

wish i had of tried harder at school!

[arbclimber]

I reckon 3 seconds fall has to be about 80ft or maybe a little more, thinking about a log dropping from a 100fter:001_huh:

 

You're well off. Would fall almost twice that far in 3 seconds. When working out the distance travelled by a falling objects you need to think about the average speed of the falling object in each second, not the terminal velocity at the end of each second. I think generally if you fall for 3 seconds in our line of work the only thing thats going to stop you is the floor.

[munkymadman]

i'm calculating it at 58.86 metres. if the acceleration of fall due to gravity is directly proportional to the time it takes until terminal velocity is reached. gravity @ 9.81

the first second the object has travelled 9.81 m the 2nd second it travels 19.62 m and the 3rd second it travels 29.43 add all these seperate amounts up and you get 58.86 m = 193ft

[Tony Croft aka hamadryad]

i'm calculating it at 58.86 metres. if the acceleration of fall due to gravity is directly proportional to the time it takes until terminal velocity is reached. gravity @ 9.81

the first second the object has travelled 9.81 m the 2nd second it travels 19.62 m and the 3rd second it travels 29.43 add all these seperate amounts up and you get 58.86 m = 193ft

 

good stuff that man!

 

So how do we work out the expected KN force of a twelve stone man falling on some slack for one second say?

 

What strain would this apply to his gear?

[Tony Croft aka hamadryad]

and then just to complicate things, how do we count the force of a pendulum swing from a limb walk slip?

[WeeDee]

good stuff that man!

 

So how do we work out the expected KN force of a twelve stone man falling on some slack for one second say?

 

What strain would this apply to his gear?

 

A 12 stone man (76kg) falling for 1 second and stopping immediatetly (which wouldn't quite happen) will exert a force of nearly 745 Newtons on the rope.

 

F = m X a

Force = mass X acceleration due to gravity

Force = 76 X 9.8 m per seconds (squared) = 744.8 Newtons

 

I hope this helps.

 

Dee

[arbclimber]

and then just to complicate things, how do we count the force of a pendulum swing from a limb walk slip?

 

I wouldn't complicate things yet if I were you. You haven't got the answer to how far you would actually fall in 3 seconds yet. The clue is in my last post.

[WeeDee]

A 12 stone man (76kg) falling for 1 second and stopping immediatetly (which wouldn't quite happen) will exert a force of nearly 745 Newtons on the rope.

 

F = m X a

Force = mass X acceleration due to gravity

Force = 76 X 9.8 m per seconds (squared) = 744.8 Newtons

 

I hope this helps.

 

Dee

 

This is wrong - sorry!

 

The answer should be 7448 N or 7.448 kN

[munkymadman]

I wouldn't complicate things yet if I were you. You haven't got the answer to how far you would actually fall in 3 seconds yet. The clue is in my last post.

 

i thought we did, not saying i got it right because i should really be applying a formula to my stab in the dark. so come on then quit dangiling a carrot on a stick in front of us and tell us. i do i have to go home and dig out my old school physics book

[arbclimber]

i thought we did, not saying i got it right because i should really be applying a formula to my stab in the dark. so come on then quit dangiling a carrot on a stick in front of us and tell us. i do i have to go home and dig out my old school physics book

 

A falling object doesn't fall 9.8 m in the first second. Its velocity at the end of the first second is 9.8m/s. Thats why I said its about the average speed in each second not the speed of the object at the end of each second.