[Blindmath] physics/mathematics problem; have a solution?

Mon Dec 19 17:20:52 UTC 2011

The area of impact will have no influence on the force experienced, the area will determine what pressure is encountered. Whether force really determines the pain, may be not, the pressure might do that (standing on your feet doesn't hurt, however push a pin in your foot with much less force and that will hurt.

I still think you probably need to know either the distance the mass is stopped over or the time to stop the mass. A wall or the ground which give very little (although small it may shift, think of how the ground can bump/vibrate as a heavy vehicle passes, e.g. a goods train passing through a rail station) will exert a greater force than something like a trampoline which gives a long way when you hit it and so is slowing you over a greater time or distance (slowing you down slower). Both time and distance could be very small (don't know exactly but may be microseconds or micro-metres), but a zero time or distance will lead to an infinite force and so should be viewed with great suspicion.

Alternative methods might be to assess the damage (e.g.. did it break a bone) and then find out what sort of force would be able to cause that damage. Another one is to see whether the force was sufficient to make you remember the mistake and so avoid it in future.

Michael Whapples
On 19 Dec 2011, at 15:32, David Engebretson Jr. wrote:

> I don't know, Michael...
> 
> I'm pretty sure it can be calculated with vectors, but it has been so long since I've done vector calculus that i  feel like i don't have the know-how right now.
> 
> What I see in my head is what I initially described; a 170 pound mass travelling horizontally at 2.5 mph.  The horizontal plane drops four feet. The mass is of sufficient height that it hits at the rim of the four foot deep 4 foot diameter hole at nearly the exact time the base of the mass hits the bottom of the hole.
> 
> Therefore, I'm assuming, all forces, horizontal and vertical, are focused on the rim of the hole when the mass hits it.  The 68" mass absorbs some kind of force at its four foot height.
> 
> The assumptions of an equally distributed mass and a 14 inch wide impact point at the mass' four foot height should have enough to figure out how many newtons of force were placed upon the object, right?
> 
> Actually, I would just need my HP48G (and some sight) to figure it out.  I'm almost certain I did problems like this in college, um, a while ago.
> 
> And Ken, we should talk... sounds like you have very similar experiences with gravity, force, and pain, that I do.
> 
> Thank you all for your comments.  I really appreciate the brain teaser and all of your insights towards it.
> 
> I've spent a lot of time norizontal trying to repair the impact point.  I keep thinking, "what would the equation look like for that situation?"
> 
> But then, luckily, I am distracted with the books I read on the Victor Reader Stream while being horizontal.
> 
> Again, thanks for your help,
> David
> 
> 
> 
> 
> ----- Original Message ----- From: "Michael Whapples" <mwhapples at aim.com>
> To: "Blind Math list for those interested in mathematics" <blindmath at nfbnet.org>
> Sent: Monday, December 19, 2011 6:01 AM
> Subject: Re: [Blindmath] physics/mathematics problem; have a solution?
> 
> 
>> Coming back to your original question, you could do it without knowing the time, however the time would still not be zero.
>> 
>> You could do it by considering what energy was absorbed in the impact and what distance the force was acting for. I guess a way of calculating the distance might be to use the size of the impression you left on the ground and the indent the ground left on you. Well may be a bit more than just what is left should either the ground or you restore your shape after the force is removed. Also it may or may not be significant, if falling don't forget that there is a change in gravitational potential energy when moving vertically, it possibly is not relevant in this case as I doubt either indent was that large.
>> 
>> Also don't forget either using time or distance, these will assume force is constant over that period and so is an average. If you want the maximum force then I am not sure it can be calculated with what is known here and probably would require you to repeat it with something to measure the pressure/force, either presenting the maximum or taking readings constantly and then you could process that. While it might be interesting to know, I am not sure I would want to do that just to find out what force was encountered.
>> 
>> Michael Whapples
>> On 19 Dec 2011, at 13:25, David Engebretson Jr. wrote:
>> 
>>> Sun lamp was fully intact.  I didn't purposely protect it with care, but it came out of the pit before I did.  No oxygen intake for me at that point. Innate mover and protector ability, I think.
>>> 
>>> Ew, I know that seeing stars thing... I was moving a photo processor once. The entrance for the photo paper was only about 4 feet tall (hmmm, coincidence?) and I was unscrewing the front cover and forgot the wall was so short.  I stood up really fast to get the next screw quickly since I was getting paid by the hour and like to be worth an employers time. Top of head bonk at 4 feet trying to move as quickly as possible vertically and horizontally at the same time from a crouching position. I saw stars and lost at least one inch of height due to neck compression. Don't think I ever healed from that one.
>>> 
>>> Still moved the processor that evening, but might have had to take a couple of days off once the concussion or whatever it was took full affect.
>>> 
>>> I think math and physics analysis in an embedded systems environment is much safer for most blind folk.  Especially if said blind people are energetic (er, stupid) enough to get him/her self in trouble with physical injury.
>>> 
>>> Aw heck, sometimes a little physical pain is good for the body.  Puts hair on your chest, right?
>>> 
>>> Best,
>>> D
>>> 
>>> ----- Original Message ----- From: "Ken Perry" <kperry at blinksoft.com>
>>> To: "'Blind Math list for those interested in mathematics'" <blindmath at nfbnet.org>
>>> Sent: Monday, December 19, 2011 4:32 AM
>>> Subject: Re: [Blindmath] physics/mathematics problem; have a solution?
>>> 
>>> 
>>>> Ha you should not be ashamed the ones that are ashamed are the ones who do
>>>> not know they can be as crazy as the sited folks.  One of my favorite miss
>>>> haps close to yours was carrying 50 pounds of roofing tile up two floors on
>>>> a rickety ladder to teach my teenager how to patch a roof.  Now this is all
>>>> after running into a power pole with the previously mentioned 50 pounds of
>>>> roofing tiles balanced on my head showing off.  Can someone come up with the
>>>> formula for a 180 pound guy hitting the ground from 5 foot 3 and a quarter
>>>> up and waiting for a 50 pound pile of roofing tiles which landed, yup that's
>>>> right on my head?  All I can say is whatever force is calculated is the same
>>>> force needed to make stars.  Anyway  I know sited people who have done worse
>>>> than us and they can see.  I am just glad that I can still do all the wood
>>>> working and you name it that I still do I would be ashamed if I gave it all
>>>> up just because of a bit of universal star creation. Hey did you break the
>>>> lamp?  I bet you didn't.
>>>> 
>>>> 
>>>> 
>>>> Ken
>>>> 
>>>> -----Original Message-----
>>>> From: blindmath-bounces at nfbnet.org [mailto:blindmath-bounces at nfbnet.org] On
>>>> Behalf Of David Engebretson Jr.
>>>> Sent: Monday, December 19, 2011 7:10 AM
>>>> To: Blind Math list for those interested in mathematics
>>>> Subject: Re: [Blindmath] physics/mathematics problem; have a solution?
>>>> 
>>>> Ken,
>>>> 
>>>> I appreciate your willingness to share.  It helps me be less ashamed of my
>>>> carelessness.
>>>> 
>>>> Best,
>>>> David
>>>> 
>>>> 
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>>>> m
>>>> 
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>> 
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