Physics and an elephant in the way
Ok, so Blackfive sent me this email this morning on how to fail a test with dignity, which you can view here.
Anyway, because I am a dork, this one has been bothering me:
Does anyone know how to solve for x if there is NOT an elephant in the way?
Blackfive tried to give me some BS answer that involved Phythagoras and Area 51 or something, but I’m fairly certain that has nothing to do with the correct answer.
Category: Politics
Well you would have to add in the force added by the C-4 used to remove the elephant
Or if a helicopter is used, the increase of the friction coeffient by the downblast.
Best one….ever.
http://3.bp.blogspot.com/_XU9x8G7khv0/Sh_xHA2tnOI/AAAAAAAAEVA/xF-oD7VUPv8/s1600-h/image003e.jpg
Height = 5m
G = 9.8 m/sec^2
Mass = 3 kg
Uinit = mgh
Ufinal = 0.5 kx^2 where k = 100.
Basically we’re looking for point where mgh = 0.5k x^2 and solve for x, which, IIRC, comes out to about sqrt 3 or 1.732 meters.
Gawd I’m such a friggin nuke.
Serious answer? x=1.72 m. Since it is a frictionless ramp, all the weight’s PE will convert to KE. so just set the PE of the weight equal to the PE of the spring.
PE of weight = mgh
PE of spring = 1/2kx^2
mgh = 1/2kx^2
(3)(9.81)(5) = 1/2(100)x^2
x^2 = 2.943
x = 1.72 m.
Can you imagine if we harnessed the brain capacity of this blog for good?
You guys rock.
Don’t feel bad, Sparky. You’re not alone. *sigh*
I think I hear Rickover’s ghost cackling evilly….
I was at sea when Rickover died. I never saw so many smiling nukes in one place underway, before or since. One of my old EDEA’s had a picture of his grave in the goat locker. Sick bastard.
TSO– LOL you just figured out the perfect nuke bait.
He was a powerful wizard. I’ve never figured out how to break his curse. And FWIW, lump me in to the sick bastard category. I have a picture of his grave as well. Accidentally found it on a visit to Arlington and couldn’t resist. 🙂
Rumor control: Is it true that Rickover once shitcanned a nuke for salting his food before tasting it?
Claymore– not sure of the truth quotient of that. Rickover was a notorious control freak. When the Navy’s nuclear propulsion program started he insisted upon complete control and oversight. To this day the whole program answers to Naval Reactors. A nuclear vessel cannot sail unless they say so. This is what I’ve heard: Rickover used to personally select all officers to go through the nuclear training program. Legend has it that he used a variety of unorthodox methods in his selection process. I’ve heard the story you mentioned, as well as a variation of it where he would ask the candidate if he salted his meat before tasting. If so then the selectee was out. I think it has to do with making assumptions. In the nuke world you do not assume, ever. Everyone has the duty and right to question everything. Another story says he would deliberately make candidates uncomfortable in the interview process by shortening the front legs of the chair so it didn’t sit straight, having a very hot or cold room, sending the candidate into a dark closet and making them answer questions from behind the door. He was an odd cat to be sure!
The next time I feel like hijacking Jonn’s board (with his permission, of course) I’ll also get Joel Kennedy over at TSSBP and see what kind of stuff the KOG (Kindly Old Gent) used to pull.
Sparky– yes please!!
You can tell this picture is probably fake because the correct solution to the problem is already 80% on the page (as per comments 4 & 5). It’s hard to believe a competent grader would not give partial credit on a 10 point question for remembering U=mgh and U=0.5kx^2
And super technically, even if there is an elephant there it makes no difference because it’s a frictionless ramp. The elephant will hit the spring and compress it the same distance.
I thought the answer was an elephant gun.
Claymore–as the rumor goes, it was a prospective Commanding Officer. He basically told the guy there was no room to make assumptions and that anyone who put that on their food before tasting it was making the same assumptions that would put the boat in jeopardy.
But my favorite Rickover quote of all: “If you have to decide whether to sin against God or the bureaucracy, choose God. He’ll forgive you–the bureaucracy won’t.”
Since the ramp is frictionless, and has no side guards, what’s keeping the 3kg weight from rebounding off the damned ramp? And that spring is not rigidly encased to ensure uniform compression. And if you look at the perspective of the ramp, and the perspective of the spring structures, they are not the same. Hence, the ramp is warped, which will result in a deflection of energy from the 3kg weight. Give the prof a ZERO for mechanical defects.
And Robotkid–never taken an organic chemistry course, have ya?
Former CNO Holloway had some insights on Rickover in his book “Aircraft Carriers at War”. Thought it was a pretty good read.
Just remember: When a nuc is bored, be afraid. Especially when we have access to glowsticks or luminous paint. Or for that matter any quantity of chemicals. When I was homeported in Alameda a couple of ELTs blew up a kitchen trying to make homemade explosives for fun.
I could have sworn that the correct answer was 42.
It’s the universal answer.
The other dangerous situation is mixing nukes and airdales, especially if there is access to alcohol. 😉
nucsnipe–I can’t confirm or deny I witnessed any alleged incidences of glowstick liquid, full radcon suits, and RC escape scuttles that opened onto a mess deck. Or a game called Danger Nut which may or may not involve a high pressure air connection, a large nut with grooves cut into the flats, and a long screwdriver. Or pus rockets (bratwurst) being fed into the TLD slot at Dosimetry. Oh yes…be very afraid of bored nukes!
My dad and two brothers are engineers (two Navy and one Merchant Marine) and would love this post. As an attorney, I’m the black sheep in the family and humbly offer the following legal answer: 1. Obtain a temporary restraining order prohibiting the reckless release of the 3-kg object. 2. Seek injunctive relief pending completion of a comprehensive environmental impact statement regarding to the habitat of all potential elephant species. 3. Have associate counsel draft products liability cause of action against spring manufacturer and ramp manufacturer in the event that Steps 1 and 2 fail.
As you can guess, I don’t join in our family dinner conversation much during the holidays.
AP, isn’t there also a “Violence against Elephants Act”? If not, there clearly should be. We can’t just willy nilly be dropping weights on surfaces which might hurt this gentle circus performers.
AW1- But we nucs need airdales to sacrifice to the great RX god in the event of a casualty.
Squidthoughts- My(hypothetical) amusement was an air drill converted to shoot 1/2 inch ball bearings. Also a good way to freak out khakis is to put a pair of coveralls on an air duct. Zip it up so it inflates and it looks like someone hanging from the duct. Got a chief and a jg in a single midwatch.
nucsnipe– the coveralls…ROFL!! Nice. Hypothetically, probes for repacking valves make excellent darts when thrown. And theoretically, a decent 9-hole golf course can be made out of nothing more than duct tape, inspection mirrors, and the layout of the plant–ladders make excellent elevated tee boxes.
My dad told me a tale, when his ship the USS Barb was in San Diego, old Hyman went on to a boat across the pier. The captain, and XO welcomed him aboard, but a young MA, demanded his ID. When the Admiral failed to produce an ID, he apparently spread eagled Rickover right there beside the pier. Every officer in sight immediately panicked and screamed for the MA to release the admiral. Once his identity was confirmed and the chaste MA saluted the Admiral, he promptly turned around and chewed out every officer in sight, then put his arm around the MA and complemented him on a job well done.
He told me that he had personally met Rickover 3 times, once for the Nuke board, once as a duty officer, and once he received an infamous Rickover ass chewing.
OK so you nuclear geniuses gave the answer to subpart (a) but not subpart (b); thus, you fail this “bar” exam. I assume that the spring will “spring” and the object will go back some distance and then comeback down the ramp again repeating this process at an ever slowing rate due to gravity, but I forgot everything I ever knew about physics a lont time ago (except for the aforementioned gravity, which, by the way, sucks). So what is the answer to subpart (b)?
Being a former Navy Sub Nuke RO I can confirm Doc’s story. Rickover boarded the boat without showing ID and attempted to walk past the quarterdeck. The duty officer said nothing but the Duty Petty Officer, whom was armed, drew his weapon and threatened to fire on the Admiral if he did not stop immdiately and show proper ID. The Admiral stopped, showed proper ID, relieved the duty officer and commended the DPO. The Admiral was revered and feared and the Nuke Navy was never really the same after he was retired.
The man here, says that subpart (b) invokes the long standing dispute over the definition of “rest” in the balk rule in college v. major league baseball. His answer is nice, but does not really tell this physics inept person the answer. So ‘gears, what is the answer?
The answer to part B is it will return to the original height and cycle indefinitely (in the absence of friction, spring non-idealities, and air resistance, etc.) If that answer drives you crazy, congrats, you think like an engineer and not a mathematician!
@NHSSparky – don’t know why it’s relevant, but I’ve actually TA’ed and graded for organic chemistry. Maybe you had lazy graders, or the higher ups were setting a “weed-out” policy which is frankly not conducive to actual learning.
This problem, however, is straight out of a non-calculus based, high school physics curriculum (or possibly a college course for non science/engineering types). I have always had my doubts about the usefulness of such courses given the contrived examples that result when you shun integrals and derivatives altogether.
This sounds like one of those equal and opposite reaction things I vaguely remember from the physics I took a lifetime or two ago.
Robotkid said “I have always had my doubts about the usefulness of such courses given the contrived examples that result when you shun integrals and derivatives altogether.”
Derivatives, however, CAN make you a lot of money if you do your research (and have a LOT of other people’s money to use to start with).
Myself, I was always more concerned with lift, thrust, and drag, and the alcohol level of the local potables. 🙂
What does the elephant urine and feces add to the equation? And, why, per AW1 Tim, does the elephant’s drunkenness, measure into the solution? Please explain the mathematical results (you can DO it in mathematical equations, but I won’t understand them: I’m a lawyer, I don’t DO math, and neither does a jury).
This reminds me of fire call for the ‘cat in a tree’. Have you ever seen a cat skeleton in a tree?? The cat in a tree is nothing a 2 1/2″ smooth bore hose line cant fix, That being said, the issue here in a non-military setting is what size hose line to move the elephant.
Our engine company would act before said restraining orders and despite the logic of ‘there arent a problems that cant be solved with a suitable application of high explosives’ would use good old water pressure. The first problem is actually a pump operator problem figuring just how much of a kick-ass master stream would move the elephant. Then propeller heads can dig into their pocket protectors and solve for ‘X’.
But perhaps you could consider laying down a blanket of mechanical foam, the better for to slide the elephant away from that darned dangerous contraption?
Maybe add a fog nozzle so as to confuse him a might?
Whatever, it’s gonna be wet!
My question, though is this: Wouldn’t mass be 3,000 since it’s 3 kilograms and weight is typically measured in grams?
I’m not a master of physics as you former Nuke types are. But I remember the Rule P. P for Plenty. as in Plenty of Explosives, Ammo, or or Alcohol (which apparently Elephants like) whatever works to move your elephant. that would take care of your elephant problem then you can call in the Nukes to solve the problem.
Mr. Chiroux, I would love to hear your stories of being a Nuke some time. I miss hearing those stories.
Silver nitrate solution. Fill water bottle. Have fight in ERLL during Maneuvering Watch going into port (particularly after long underway–end of Westpac is even better.) “Victim” goes topside. Sunlight hits silver nitrate still on guy’s face and clothes.
Don’t even get me started on the various and hilarious uses of Prussian Blue or neolube, particularly on sound-powered phones and reactor periscopes.
And Robot–when I was in college my Chemistry professor had a habit of posting some of the more “unique” answers outside his office. Amazing, really.
Robert–“No Balls” position of the scram switch with the mark erased and put well past where the reactor would scram, then get gullible person to try to go past the mark. I always loved that story.
Can’t resist weighing in on this, so here goes.
Well you would have to add in the force added by the C-4 used to remove the elephant. **Personally I wouldn’t use explosives to remove said “object” from ramp. The damaged surface would no longer be of use until said surface was refinished to the original spec’s otherwise the weight will a)slow considerably or b)come to a complete stop. Coefficient of friction? Once surface(s)is(are)restored, use of moly grease on both surfaces should greatly reduce the coefficient of friction.
Or if a helicopter is used, the increase of the friction coeffient by the downblast. **Nix that…unless you are prepared to add a suitable surfactant to blend with the air and properly mixed ratio before reaching the rotors….Use .751 to calculate the unknown density?
OK so you nuclear geniuses gave the answer to subpart (a) but not subpart (b); thus, you fail this “bar” exam.~~~So what is the answer to subpart (b)? ** Multi-part solution would be; a) tempt elephant with food (ie bale of hay)and lead it out of the area or b)Force it out of the area with large volume of fresh water preferably (7.34 lbs/gal) or if unavailable recommend sea water (approx 9.4-10.2 lbs/gal). Diameter of fluid delivery system per FXCO’s recommendation except, my choice of equipment would be use a quick attack or foam pumper to deliver fluid column…
Well, as we always said about demolition problems… the more C4 you use, the less Physics you need know.
What if you use a mouse? How high does the elephant jump?
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