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fencing physics   
02:18pm 08/05/2007
27 April 1989 - updated 11 December 1994
[Disclaimer: All similarities between real fencers and characters in this exam are purely intentional and completely without malice.]

Instructions: Answer all questions. Be sure to show your work (including, where appropriate, free body diagrams). Don't screw up the math. Except as noted, you may neglect air resistance and friction.

1. A 2m tall Italian epee fencer loses his last repechage bout by being pushed off the end of the strip (standard 14m length). He knocks his mask straight into the air and simultaneously kicks his reel, which had been positioned at the end line, towards the other end of the strip. The mask just touches the 6m high gym ceiling before starting its downward descent. The fencer sees the reel barely clear the head of the 1.75m tall referee, who is standing in front of the scoring table recording the result. Just as he is knocked unconscious by his plummeting mask, he sees the reel land at the feet of the chairman of the Directoire Technique, who had been watching the bout from the far end of the strip.
a) How long does it take the reel to reach the ground?
b) Calculate the initial magnitude and direction of the reel.
c) How long will it take after the fencer regains consciousness until he is expelled from the competition?

2. Claus Block is bouncing up and down two meters from his opponent's end of the strip. His reel has slipped to 1.5 meters in front of his end line, and the reel cord is attached to his waist 1m above the ground. The mass of the exposed portion of the reel cord is 500g. A standing wave of three loops is being produced in the reel cord.
a) If Claus hits the ground 10 times per second (it's the finals), what is the tension in the reel cord?
b) Assume that the tension in the reel remains as calculated in part (a). Where would Claus have to stand and bounce, relative to his initial position, to produce a standing wave with only two loops?

3. A brand-new Uhlmann epee point is constructed such that the total travel is exactly 1.5mm, and it just passes the 0.5mm shim test. When a test weight of 750g is gently dropped onto the tip, the scoring machine light comes on. After the machine resets, the light remains off. However, any further depression of the tip causes the light to come on.
a) Calculate the spring constant (k) for the point spring (you may neglect the mass of the tip).

A Russian point is dimensionally identical to the Uhlmann point, but friction in the point produces an extra 1N of resistive force. Since its owner cannot readily fix his weapons, the point spring must be strong enough to lift 2kg (as above), to ensure that his weapons will never fail on the strip.
b) Calculate the spring constant (k') required for this point spring.

The two weapons are fixed horizontally, tip to tip, then the retaining screws are removed to allow free movement of the tips. The two tips are displaced 0.5mm from their equilibrium position and then released.
c) Calculate the frequency of the resultant SHM. (Assume that the mass of 1 tip is 1g and that both tips move together.)

4. Yuri Rabinovich and his long-lost identical twin brother Pavel (each with mass 65 kg) are fencing sabre. With weapon arms half-extended, they launch simultaneous fleche attacks and lock bell guards in mid air. Just before impact, each is traveling at a speed of 5m/s. When their bodies pass, the centers of mass are 1m apart. The bell guards remain locked and their arms extend to full length (adding 1m to the distance between the centers of mass).
a) What is the angular momentum of the resultant tangle immediately following the collision?
b) When the arms are extended, what is their rotational frequency in revolutions per second?

5. In the midst of a team free-for-all, Frank MacKenzie (mass 90 kg) picks up Lara Tomasso (mass 65 kg) and attempts to hold her at arm's length (this would put her center of mass 1m from his center of mass). Frank has enough upper body strength to support a mass of 25kg in this manner.
a) Frank, being an engineer, starts to spin. After accelerating for 5 seconds at a constant rate, his arms are forming an angle of 5 degrees with the horizontal. Find his angular acceleration.
b) At this same acceleration, how long will it take until his arms are 2.5 degrees from the horizontal?
c) How long before his arms are perfectly horizontal?
d) How long will it be before Lara throws up?

6. a) The maximum length of a foil blade from tip to bell guard is 90cm. Taking the pivot point to be at the bell guard, calculate the torque produced by a force of 20N applied perpendicular to the blade at the following distances from the tip of the foil:
1) 85 cm
2) 50 cm
3) 10 cm
b) If you are able to produce a torque of 10Nm around your own bell guard, calculate the resultant torque around your opponent's bell guard if your blades are pushing at right angles to each other and the intersection point is 10 cm from your bell guard and 45 cm from your opponent's bell guard.

7. Assume that a foil blade (not including the tang) is a uniform rod of length 90cm, diameter 5mm and mass 150g. Your opponent beats your blade sharply 40cm from the tip, breaking the blade. She then immediately does a circle disengage and hits the free end of the broken piece with a 20N force for .01 second. Calculate the rotational frequency of the broken piece of blade as it spins off end over end. (The rotational inertia, I, for a uniform rod of length L is 1/12mL^2, with the axis of rotation at the center of the length of the rod.)

8. A golf ball of mass 46g hangs from an ideal string 1m in length. A diligent epee fencer practicing point control strikes the ball with sufficient force to cause the string to form an angle of 15 degrees with the vertical.
a) What is the velocity of the golf ball immediately following impact?
b) How long after impact will it take the ball to reach the point where it is closest to the fencer?

9. Peter Westbrook (mass 70kg), having temporarily forgotten the end-of-strip rules in the heat of the finals, retreats rapidly off the end of a raised piste 0.30m high. Fortunately for Peter, the regulation run-off incline of 2m has been included.

Unfortunately, he trips and ends up rolling ignominiously the entire length of the incline. Assume that Peter's body approximates a cylinder of 50cm diameter as he rolls without slipping down the incline. Further assume that he is not moving horizontally when he hits the top of the ramp.
a) If Peter is making 2 revolutions per second when he reaches the bottom of the incline, what was his angular momentum when he hit the top of the incline?
b) What torque is required to stop Peter's rolling at the bottom of the ramp in 1 second?

10. Isabelle Hamori shrieks in the heat of combat at 13,000 Hz. The gym is set up with pairs of two meter wide strips three meters apart, with six meters between each pair.
a) If Isabelle is fencing in the middle of strip 11 at the far end of the gym from the Bout Committee table, which is 10 meters from strip 1, how much longer will it take the Chairman of the Bout Committee to wince than Isabelle's referee, who is standing halfway between strips 10 and 11? (This is at the 1988 Chicago Nationals, where the ambient temperature is approximately 40 degrees C. Take the speed of sound in air at 20 degrees C to be 340 m/s and remember that the speed of sound is related to the square root of the temperature in degrees Kelvin.)
b) Isabelle's opponent is MJ O'Neill, also known for her dulcet tones on the strip. MJ screeches while fleching at Isabelle, who attempts to retreat, at full voice. The referee, who is maintaining his original position relative to Isabelle, notices that the combined shrieking is producing 2 beats per second. If MJ screeches at 12,980 Hz, what is her minimum velocity relative to Isabelle?
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The Talking Tactile Tablet system   
08:27pm 29/06/2006
mood: in a great mood
Reading slashdot's main page for today I read the title of an article that said "THE BES PRODUCT DESIGN OF 2006", about an audio system for visualy impared people, instead of using Brail...what I find ironic is that the porpuse is to discribe images to the blind. Now if some one has lost their sight after bein able to see I can see where this is usable, but how in the hell do you discribe how something looks to some one that was born unable to see...thinka bout it, when you discribe you use metaphors and other similes, its almost a moot point hearing a description as it is reading it, if you have no idea what the image in question is being compared to you will end up more confused than aided.

11:46am 19/06/2006
  so I'm bored just finished doing thousands of calls for job interviews, connection set ups for the new lair, and other shtuff; and since I'm not playing SKIES OF ARCADIA for a whole day, I'm posting a random blahber into this.
best things so far of Columbus:
1-easier to get around and better connected road wise
2-alot of family and drinking (I don't think I might remember this summer much again)
3-bigger room
4-non crappy actually owned car by yours truelly
5-watched finaly "final fantasy: Advent children"
6-stealing internet from neighboors since they have it open
down sides:
1- missing most of the world cups games since ABC only shows them on weekends damn bastards.
10:05pm 19/12/2005
  153....hmmm they should rise the line to 155....Collapse )  
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early christmas salutations   
01:15am 19/12/2005
  just wanted to say afew words, happy birth of the sun-god on the this time of celebration, and may saturn and Dionysus look upon your festivities on this yule....oh and where is jesus in all of this? his birth was durring the summer learn your modern holiday's roots.  
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month an eyes   
01:03am 16/12/2005
  look for the colors of your eyes and the month you where born and see what it says (bored though I would share something)Collapse )  
11:24pm 18/11/2005
  not recomendable, but I've given ride to about three hickhikers in the past two weeks. other than that there isn't much going around, except DECEMBER 1st is the next slam no YOUTH slam this month because of thanksgiving, and if the slam on the first is equal to the last one, it will be a slam not to miss. hope to see as many of you there  
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thursday, at 6pm see you there   
11:31pm 20/09/2005
  you might ahve seen the bulletin I posted in myspace but jsut in case
6pm pre game open mic workshop type of thing
Jared, Katie, and I will be around in the merc table, entrance, helping around with stuff, and full of information....
7:30 youth slam competition, followed by Feature ADAM STONE i bleive, and OPEN MIC in the end. the DJ will be TOM.
entrance is $4.00, and just for the ones that FORGET its the 1ST and the 4TH of every thrusday...nto the last the 4TH...yes people some months ahve 5 thursdays in it.
yeah still got one...for other reasons now   
09:42pm 16/09/2005
  I'll be mostly posting info here my acutaly one journal is in Greatetjournal....anyways, I just wanted to share that food service is fucking horrendosus to work in...and oddly I got two jobs in it, UNOs and Eu Bon Pain in Thayer...from 6am-2 pm and from 5-9 UNOs....yeah thats what i call busting your ass...
either way
also monday's at the black rep is open mic, and soon they will be having slam competitions, and if you win those competition you get to be in the providence team as well[not effective yet]...other news will be later posted

hope to see you at AS220 this coming thrusday.
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oh yeah   
07:28pm 29/06/2005
  so I didn't get mug or shot and I'm returning back 2morrow around 11 at logan airport...but I did saw a dead guy with for bullet shots on the head...couldn't take pictures...the quillies were around  
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quick update   
12:27am 17/06/2005
  IN ES, its only 12 right now so that would make it 2 over there. I bought a web cam for 24 bucks here lol, already saw mr. and mrs. smith...hot movie, ECVERYTHING looks so different from when i left...and its sadding to see what I've seen yet happy. Its fun thought...I'll be back the 30th at 11:45ish at logan airport....I'll take photos and show you all what i meant.
have fun people
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quick recap of a week and two days.   
11:12pm 08/06/2005
  monday: memorial's day, drove around, bought shirts and played b-ball in NP. Lifted wieghts to see who would do the most weight.
Tuesday: exams, rested and slept.
wensday: yearbook, exams, harassed people for signatures, bay queen. more harassament, dance, food, dance. "SAY WHAT?" JM's car. lost in massachussets.
Thursday: Practice at school don't remember anything else
Friday: Buttler for survey, errands, Prom, Poll hall "the greenroom", limo rides
Sat: Sick as hell, frozen on the ground, muscle spams, flow of the ass, felt like I was reaping a part.
Sunday: rested and cured
Monday: convocation and slept
yesterday: practice at cathedral, dropped off the chorus outfit, liturgy, banquett at venus de milo, picture harassment.
TODAY: Road trip to Sixflags, Driving in a mixture of pat and alessio style, SIXFLAGS, rides, waterpark, Roadtrip back, call from adam milniki, called alessio(did picked up) for a few minutes, drove to clacks poll hall and played, dropped people off, rest now...
tomorrow-wensday: graduation, Lunia's party, chilling saturday, getting ready sunday, emmanuel monday and tuesday, packing tuesday, El Salavador wensday morning arriving at noon....out of contact for two weeks. might get shot, might get in car crash, will get drunk, high and in bar fights (with old friends' new life style)will have fun and will have dreadfull time, will surf, will play soccer at stadium, will not sleep one bit....its gona be a good graduation present.
laters...off to sleep till 3 pm
01:32pm 03/06/2005
  - think of the first word that comes to mind when you think of me. (don't tell me what it is)

- run a google image search on that word

- reply to this entry and post that picture

- put this in your journal, so others can do the same
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its been a great week   
11:29pm 01/06/2005
  I will update in a while about the whole week but right now I have a recomendation.
If you ever get a chance watch "innocent voices" is a movie about the civil war that happened in my country between 1980-1992. Its good movie to watch, take my word for it.
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Dorm what?   
03:16pm 28/05/2005
  so I was reading this article on Dorm life...and as I read through it I remembered the show undressed in MTV about 3 or 4 years ago....and I pounder if it will be the same? lmao...oh yeah bored right now lol  
Fun Fun Fun...   
04:11am 28/05/2005
  so today started with driving to exams on the mini vana nd parked right next to the gate....did my analysis exam to which I did not study yet I know I passed cuz all year i did not learn a single new thing. Well after that it was hour of lunch, and then Vid exam....for the majority of the time I played pokemon as well as durring analysis. It was quite fun because we saw other people's porject and I ahve my two final ones in a DVD so people can see it. Drove back home and went back to spun for the last one ever. it was Funny seeing as Ashley bray made a power point, and I looked as if I was batting for the other team, but I'm not. It was sad cuz it was out last Spun but it was fun at the same time. Headed back home and chilled for a while untl my mother and father left for Boston for the night, and I dropped them off. After that I went to Mr. Calderon's gallery for the poetry reading. Some of the girls from Classical I think they were, they were hot, there was two I would of like to get to know. Anyways the show was done and finished around 9:30 so I headed to Pat's house and I chilled for about two hours, played texas hold, talked, and watched Ernest goes to camp. that man went every where really. In the middle of it I left for home. but when I got home and online I was told there was a get together in Coventry exit 6a and so I ehaded there at 12:30ish. It was fun, Chilled, drank, made noise with a 12 string, was there while a girl puked for an hour straight, met cool new people, and finaly saw anita after long as while.
I left with Jilly around quater of 3 and dropped her off as soon as possible and as careflly as possible while we heard that there was an accident on 95 south exit 13 or something near it. It was interesting. well I drove back home safe and sound and now I'm off to bed.
last day   
03:38pm 25/05/2005
  ok so today was ofcourse the last day of senior classes, which was filled with alot of school shirt signing. as of today I have two shirts signed. at the beggining of school Jess wrote the epilogue in my right arm in compu lab. Then I hunted down people so they would sign it all day long. gave shelly the photos that she wanted, and amy her pic. last lunch ever was fun, more signing and free pizza. also the last "OOOOOOOOOOOO" was done and it need to be done before leaving. last class what every one dreaded because it was analysis was alot of fun and it went by way too fast for being that class. Lorin took a pic of that class and I want a copy. I drew a tropic island on Cassie's leg and every one was busting her cuz she was in a very exposing possition lmao. the day ended and every senior was screaming and yelling it was over. that was fun. then the last chorus rehersal I'm gona be in. where Jm drew nippels in Dave Polce's shirt and then polce drew tits on it. with that we were laughing instead of signing and then JM drew a di<k in between, that got every one going. we got an appriciation talk from mrs. Fonts and some of the girls were crying. we sang start spangle bananas and we chilled in the chorus room for a while. Seeing as its the chorus people it was interesting, polce and Laura smacking each other's ass, I grabbed laura's boob couldn't leave school without doing that lmao and more hunging was done. yeah so now I'm free of classes only have few exams to take and thats it. bay queen. prom can't wait for that, its gona be awesome. and what fuck is senior convocation???? and ofcourse graduation ceremony.  
11:17pm 23/05/2005
  a little survey for yous to fill lolCollapse )

The Keys to Your Heart

You are attracted to those who are unbridled, untrammeled, and free.

In love, you feel the most alive when things are straight-forward, and you're told that you're loved.

You'd like to your lover to think you are optimistic and happy.

You would be forced to break up with someone who was ruthless, cold-blooded, and sarcastic.

Your ideal relationship is comforting. You crave a relationship where you always feel warmth and love.

Your risk of cheating is zero. You care about society and morality. You would never break a commitment.

You think of marriage as something precious. You'll treasure marriage and treat it as sacred.

In this moment, you think of love as something you thirst for. You'll do anything for love, but you won't fall for it easily.

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a bit late huh Jill? lol   
02:54pm 20/05/2005
  01. Reply with your name and I will write something about you.
02. I will then tell what reminds me of you.
03. If I were to apply an o'clock to you, it would be...
04. I will try to name a single word that best describes you.
05. I'll tell you the most memorable moment I've had with you.
06. I'll then tell you something that I've always wondered about you.
07. Put this in your journal.
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04:57pm 19/05/2005
  its beena good up to now. the classes themselves were eh ok, had two frees one last but didn't leave, and because of it I saw Pat O'donnel and jimmy, they were visiting. and I taunted Alex it was funny, but even so more when say goes "WHAT? YOU ONLY HAVE FOUR MORE DAYS OF CLASSES?" cuz apperantly john didn't tell her, so she started to spazz. She did indeed finished her box. After I walked around with Heather and got attacked by amanda malkasian for reasons I did not knwo at the time and that I will not tell now...still was funny righT amanda?
Well school ended right after and i was walking around, and had a small talk with Julia, followed by sitting on the edge of the big front stairs...that was fun. I was told to get off by I think mrs. Murphy didn't see who it was, cuz i was going down anyways.
At the box office the Funniest thing was said. I saw talia, Bailey, and Christina M. so I was talking to them for a little, I mention having last day of classes on the 25th and she goes "why? where you going don't you have exams?" cuz she thought I was Junior and I burst out laughing, she now knows she's been lied to for 3 years lol and that I'm indeed a senior. Chilled with Bianca and meg and this girl who is girlfriend with the pete I take itlaian with idk her name. and I got her the star wars theme song stuck in her head. walked home and talked to Mike pagano cuz he was working on his house and right there I saw heather and John(freshman) and we rode to LSA and then headed back home witha ride form heather. it was an overall fun day.