Sponsored By
ROCK HARDWARE
|
Chockstone Forum - Accidents & Injuries
Report Accidents and Injuries
Topic
|
Date |
User
|
Danger Area Below Cliff Rescue |
31-May-2012 At 3:03:34 PM |
sbm
|
Message |
I'll have a go at a back-of-the-envelope.
The gravitational energy in a 9kg rock falling 30m is mass * gravitational acceleration * height:
mgh = 9 * 10 * 30 = 2700 kJ.
The splitting into three doesn't really make a difference as you'd also split the kinetic energy into three so the distances are the same.
The rock hitting the ground is a very inelastic collision, lots of energy goes into the boom and the crater and breaking apart the rock. Let me pull a number completely out of my arse and say 50% gets converted into kinetic energy.
1/2 mv^2 = 1350
rearrange and get v = sqrt(2*1350/9) = 17 metres per second.
Maximum range you get from launching a projectile from flat ground at 17 meters per second is
v ^ 2 / g = 17^2 / 10 = 29 meters.
Hey, looks like your rule of thumb came out pretty well!
This also ignores the bouncing and rolling after fragments hit the ground.
Being a bit more formal with the maths, it turns out the maximum distance D a rock could bounce upon hitting the bottom of the cliff, is D = 2 * a * h, where h is the height it fell and a is the percentage of energy converted into kinetic energy in the impact. Assuming a is 50% or 0.5, kierenl's rule of thumb is spot on. |
Home | Guide | Gallery | Tech Tips | Articles | Reviews | Dictionary | Forum | Links | About | Search
Chockstone Photography | Landscape Photography Australia | Australian Landscape Photography | Landscape Photos Australia
Please read the full disclaimer before using any information contained on these pages.
Australian Panoramic |
Australian Coast |
Australian Mountains |
Australian Countryside |
Australian Waterfalls |
Australian Lakes |
Australian Cities |
Australian Macro |
Australian Wildlife
Landscape Photo |
Landscape Photography |
Landscape Photography Australia |
Fine Art Photography |
Wilderness Photography |
Nature Photo |
Australian Landscape Photo |
Stock Photography Australia |
Landscape Photos |
Panoramic Photos |
Panoramic Photography Australia |
Australian Landscape Photography |
High Country Mountain Huts |
Mothers Day Gifts |
Gifts for Mothers Day |
Mothers Day Gift Ideas |
Ideas for Mothers Day |
Wedding Gift Ideas |
Christmas Gift Ideas |
Fathers Day Gifts |
Gifts for Fathers Day |
Fathers Day Gift Ideas |
Ideas for Fathers Day |
Landscape Prints |
Landscape Poster |
Limited Edition Prints |
Panoramic Photo |
Buy Posters |
Poster Prints
|
|