Help working out the moving of volume and stone (fictional/theoretical)

Jun 2013
6
0
Heya everyone, I am a fan of various fictions and I like to try and find out how "physically" impressive some characters superpowers are. Admittedly being a fiction not all physical processes are likely being followed but it can be interested to try and find out various speeds, forces and how some powers would interact with the world were they real and under our laws.



The reason I joined is because I am not great at math or physics and I needed some help determining some values or how things work, heres the question and the scenes I am referring to;



http://www.youtube.com/watch?v=dpWP9e-iQj8&t=1m53s



Now what I want to know is, how much force and what physical processes would be required to push his claws into that stone (for the sake of argument lets assume its granite) ?


My assertions would be that he has to somehow move the stone inside the block for his fingers to fit, therefore pushing it back and the surface area/volume of his fingers would be relevant to the calculation, as would the density of granite?

So assumptions I will allow are;

-Raziels three claws that he inserts into the rock have a volume roughly around 500 centimeters cubed (Their a lot bigger than the human hand)


-That stone block is granite.



So would I need to calculate the force/jouls etc required to move 500 cc+ of granite?

Thank you for any aid, I apologise if a fictional character is not what you would generally be interested in trying to calculate and I apologise if fictional and theoretical ideas are not allowed.
 

topsquark

Forum Staff
Apr 2008
3,049
648
On the dance floor, baby!
Heya everyone, I am a fan of various fictions and I like to try and find out how "physically" impressive some characters superpowers are. Admittedly being a fiction not all physical processes are likely being followed but it can be interested to try and find out various speeds, forces and how some powers would interact with the world were they real and under our laws.



The reason I joined is because I am not great at math or physics and I needed some help determining some values or how things work, heres the question and the scenes I am referring to;



http://www.youtube.com/watch?v=dpWP9e-iQj8&t=1m53s



Now what I want to know is, how much force and what physical processes would be required to push his claws into that stone (for the sake of argument lets assume its granite) ?


My assertions would be that he has to somehow move the stone inside the block for his fingers to fit, therefore pushing it back and the surface area/volume of his fingers would be relevant to the calculation, as would the density of granite?

So assumptions I will allow are;

-Raziels three claws that he inserts into the rock have a volume roughly around 500 centimeters cubed (Their a lot bigger than the human hand)


-That stone block is granite.



So would I need to calculate the force/jouls etc required to move 500 cc+ of granite?

Thank you for any aid, I apologise if a fictional character is not what you would generally be interested in trying to calculate and I apologise if fictional and theoretical ideas are not allowed.
The granite would probably shatter so we would need a softer rock, such as limestone perhaps. The density of the rock will not change so we also need a way for the material to get out as he pushes the claw in. I have no advice on this one. (And, of course, while he's pushing the block there will be a recoil due to Newton's 3rd, and he doesn't show that.)

That's my "stab" at it. :)

-Dan
 

ChipB

PHF Helper
Jun 2010
2,367
292
Morristown, NJ USA
The density of the rock is really not relevant - it's the indentation hardness of the material that's important. He punches the rock and creates a hole that gives him a way to grasp and pull the stone. There is a measure of indentation harness of materials called the Brinell Hardness Scale that describes the force required to press a round ball of a given diameter (typically 10mm) into the material. The formula that they use is:


where F = normal force applied in newtons, D = diameter of the indenter in mm, and d = diameter of indentation in mm.

I doubt that this applies terribly well to the situation in the video, but just for fun here's a back-of-the-envelope calculation: to completely push the ball into the material means D=d, and we can rearrange this to become:


Mild steel has a hardess of about 120 and tool steel around 1500, so we can probably guess that granite might be a bit softer than tool steel - let's call it 1000. If we assume that the character's claws are each about 20 mm in diameter we get:

F = (1000 x pi x 20^2)/0.204 = 6.2 million newtons, or about 1.4 million pounds.

This is much greater than the weight of that block, so he'd be better off just pushing it rather than using this technique. Also note that his claws must be made of a material much harder than the stone - perhaps diamond!
 
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Jun 2013
6
0
The granite would probably shatter so we would need a softer rock, such as limestone perhaps. The density of the rock will not change so we also need a way for the material to get out as he pushes the claw in. I have no advice on this one. (And, of course, while he's pushing the block there will be a recoil due to Newton's 3rd, and he doesn't show that.)

That's my "stab" at it. :)

-Dan
I see so granite would shatter? Would it be possible, lets say this is limestone for the material hes pushing, simply to push out inside the block and make space within? e.g., if he warps the stone inside enough with his claw going in, the crushed material inside simply pushes outwards, sorry I am not so articulate when trying to describe a physical process.



Also what do you mean by a recoil?






The density of the rock is really not relevant - it's the indentation hardness of the material that's important. He punches the rock and creates a hole that gives him a way to grasp and pull the stone. There is a measure of indentation harness of materials called the Brinell Hardness Scale that describes the force required to press a round ball of a given diameter (typically 10mm) into the material. The formula that they use is:


where F = normal force applied in newtons, D = diameter of the indenter in mm, and d = diameter of indentation in mm.

I doubt that this applies terribly well to the situation in the video, but just for fun here's a back-of-the-envelope calculation: to completely push the ball into the material means D=d, and we can rearrange this to become:


Mild steel has a hardess of abouit 120 and tool steel around 1500, so we can probably guess that granite might be a bit softer than tool steel - let's call it 1000. If we assume that the character's claws are each about 20 mm in diameter we get:

F = (1000 x pi x 20^2)/0.204 = 6.2 million newtons, or about 1.4 million pounds.

This is much greater than the weight of that block, so he'd be better off just pushing it rather than using this technique. Also note that his claws must be made of a material much harder than the stone - perhaps diamond!
I see, if only someone could tell him what a wally he is for making more work for himself, those numbers are significantly bigger than I imagined (Worried) but then the calculation suggests pushing a round ball doesn't it? Wheras his claws are more pointed and may excert more pressure due to being sharp so maybe it requires less force?

What you said gives me somewhere to work from thats for sure. Thank you both very much for your help and time.

As another note how heavy would you say that block is? As an estimate if it was limestone?

Additionally, how heavy do you think this is;

http://www.youtube.com/watch?v=0QMNFZGh3pA&t=2m40s

This large obelisk, possibly made of limestone, granite or marble as a number of estimates. Marble and limestone are both common for real obelisks no?


Then from there, how do you think I could calculate how much strength/force etc he required to flip it over the way he did? he sort of brings it to his chest and pushes it over, using the pivot of the obelisk to move it. If he had lifted it up normally I could have estimated some force from weight but since he used a pivot I don't know how much effort/force he would have to excert considering its size?

Thanks again for your aid gentlemen.
 

topsquark

Forum Staff
Apr 2008
3,049
648
On the dance floor, baby!
Also what do you mean by a recoil?
If you look at the part of the video where he's pushing the block. The block is shoved around, but he didn't move or even seem like he had to. If he's exerting a force on the block then there must be a force acting on him from the block. ie. He gets pushed back when he shoves the block...recoil.

-Dan
 
Jun 2013
6
0
I see now I think I understand. So if hes pushing the block, opposite equal reaction suggests he should be pushed back? Maybe its just part of his "supernatural" ability to be especially steady/sturdy or something.
 

ChipB

PHF Helper
Jun 2010
2,367
292
Morristown, NJ USA
...Wheras his claws are more pointed and may excert more pressure due to being sharp so maybe it requires less force?
True, but my calculation is probably so far off the mark from reality that it really doesn't matter!

As another note how heavy would you say that block is? As an estimate if it was limestone?
I'm guessing that the cube is 3 meters per side, or 27 cubic meters in volume. The density of limestone depends on the type - it can vary from about 2100 to around 2900 Kg/m^3. So the total weight of the block is between 56700 Kg and 78300 Kg, which is 125,000 pounds to 172,000 pounds. If you think about the point Topsquark made regarding reaction forces - if the creature doesn't weigh at least that much then pushing on the block without having something in the floor to keep him from sliding backwards (toe hooks of some kind) would only result in pushing himself backwards.


Additionally, how heavy do you think this is;

http://www.youtube.com/watch?v=0QMNFZGh3pA&t=2m40s
It looks to be about 3m x 3m x 10 m, or 90 m^3. Using the above density for limestone it would weigh somewhere between 415000 and 575000 pounds.

Then from there, how do you think I could calculate how much strength/force etc he required to flip it over the way he did?
He needs to be able to lift half its weight, so 1/2 the values above.
 
Jun 2013
6
0
Thanks Chip again on the information.


So where to go from here, I wonder how we could make that figure more accurate. I think your calculation above is a good starting point, because in some way he would still require the ability to push into the stone, the only different is his fingers are conelike and sharp rather than a sphere.



Any way of changing some figures around in that working you made to co-inside with a cone rather than a sphere?

Obviously, pressure at the tip of his claw will be significantly higher than the surface of a sphere or the outside of his "cone" if you will.
 

ChipB

PHF Helper
Jun 2010
2,367
292
Morristown, NJ USA
Any way of changing some figures around in that working you made to co-inside with a cone rather than a sphere?
I know of no way to do this calculation - you would have to run the experiment. The whole calculation is based on an assumption that the Brinell Hardness formula applies to the sceanario of completely pushing his fingers in, which is most likely wrong. As has already been stated - under these forces the block is likely to fracture, not act like a big piece of jello as in the video. So there's really not much point in trying to get more accuracy in a totally unrealistic calculation.
 
Jun 2013
6
0
Ok thanks for your aid.


I take it in reality as you said, even a block of stone would fracture in such a way from him stabbing into it? I wonder if my assumption of it being stone could be wrong and it could infact be metal? would a block of iron be moved more realistically?
 
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