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So I'm starting my EE today, in physics. My research question is:
"Is it more beneficial for a rugby player to increase velocity or mass in order to increase his/her effectiveness in the tackle?"
I picked it because its personally interesting, and probably will be fun to research. It's also probably going to have a shitload of problems considering controlled variables (height, leg length, tackle technique, etc). What I basically plan to do is to compare the change in momentum (by the equation P=mv) and kinetic energy (by the equation Ek=1/2mv^2) by changing mass and velocity. Obviously since I can't change my own mass or top speed on a whim, I need several different players of various sizes and speeds. This is where the controls get out of hand. How will I control things like height or stride length? What about tackle technique?
In terms of actual quantitative measuring, I don't think I'll have any problems. The way the experiment will be set up is as follows:
A tackle bag will be placed on an X on the pitch. Subjects will take as long of a run up as they need to get to full speed, at which point they will attempt to hit the bag as hard as possible and knock it back as far as possible. This process will be recorded using a camcorder, and the speed of the moving players will be analyzed using the program called DARTFISH (http://www.dartfish.com/en/index.htm). The masses of the subjects will be taken on-site just before they begin the experiment.
My problem here is probably not going to be my method in gathering data, but trying to process that data so that I can come up with a justified conclusion. If I find that my lack of controlled variables results in an invalid conclusion, I'll have to resort to using a microcosm-type experiment under laboratory conditions. One idea that my advisor had was to use a pendulum with a sphere attached, and using it to hit a clay block, and using the same DARTFISH software to analyze it.
Another interesting point that my advisor brought up is that this sort of research has without a doubt been conducted before. A quick Google search doesn't show too many relevant results, but maybe I just need to search harder. There are probably a lot of universities and professional teams that conduct this kind of research using professional sport scientists and biomechanics experts. I'd personally be very surprised if the All Blacks haven't done something like this. If I can get access to this sort of research, it would help me a lot.
Basically, the reason that I'm writing this is to get feedback or ideas from you guys. From what I've read, a lot of you have done, or are doing, the IB Diploma, and could give me some advice. Anything and everything would be highly appreciated  .
Sorry this is really disorganized, I was trying to get all my information down. If you have any questions or comments just make a post below.
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Katowice25012 Posts
This is a super sweet question, I find that research done when someone has a passion about the topic is always much better than not.
To find if any more writing has been done on the same topic google probably isn't your best bet (although I have found good stuff on scholar a few times). Have you been digging through journal archive databases you have access to through school? I suggest searching through whatever physics/engineering banks you can find for similar topics, surely someone has tried their hand at something like this before somewhere. In general, I've found that papers written on subjects like that are pretty half-assed so it would be great if you could find past work on it and sum up their shortcomings and how you can make it more conclusive.
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Seems to me like your biggest problem will be coming up with an accurate way to measure "effectiveness of the tackle". Stuff like height and technique should be taken care of as long as you have a big enough sample. And yeah I'm sure this kind of thing has been studied before, although I'm not really sure where it would be published. It might be that a lot of teams study it and don't publish their results.
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United States24701 Posts
Be careful not to put your subjects at risk.
Regarding a theoretical approach you should probably talk about how p=mv and ke=.5 m v^2 are different.
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The was a TV show that explain which one was better O.o
Don't remember the show but it was something like: "Science of Sports" (in French, it was Science du Sport)
It was a series of about 5-6 episode.
One of the test show that a collision done by a Sumo was less powerfull then a collision made by a Americain Football player (with lots of data and all to prove it).
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Well I am sure that increasing velocity is better with some initial v's and m's and not as good with others. You have to do some relational math to see for which values of v and m will increasing v raise the force faster than m and for which values of v and m that m raises the force faster. Then you can decide which m's and v's are relevant to the spectrum of humans you wish to study. That's the forming a hypothesis step that, if i am not mistaken, you skipped. Also there is nothing that will allow you to measure their effort so small changes will not be able to be recorded.(have them hit the bad multiple times obviously.)
Having said that it sounds really fun, but pretty time consuming on the research side. Just grab a math(or physics) teacher at your college and I'm sure he can help you figure out the v's and m's part as long as you have clear equations relating what you need and an outline. (although it kinda feels silly if you let someone else do all your theoretical work i.e. the brain work)
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Increasing velocity is more effective as it will transfer more energy: (1/2 m v^2), but a light, quick person will receive a greater impulse after the tackle, and likely hurt himself. The mass of the defender will also be very important because a heavy person takes more energy to move.
Now, Physics is a very difficult topic to be writing an Extended Essay on, but don't be discouraged, a friend of mine got an A on his He wrote about fuels and their practicality (accessibility, stored energy per kilo) and their impact on the environment.
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Having played rugby during my college, the first thing i thought about your subject is "what post is your player assuming?"
I mean as a pillar you'll have to tackle players from the pack hence you need to be bulky.
When playing in the wing speed is your main asset, mass is after all useless if you cant reach the slim little fu**** running like a bullet along the line.
My personnal experience: as a 2nd line of roughly 85kg i was fast enough to catch most players during a match however during rough matchs (hear: while playing against a real team by opposition to our amateurish one) i often got knocked down by heavier players.
This kind of research it has obviously been done before, there are machines available to help training tackle . Maybe you could find how they are set and used.
Last week i read an article about a new machine designed to help the France national rugby team to train melee (and to learn how to prevent backbone injuries), you wont be able to find information on this machine but the engineers and scientist involved in its creation were mentioned, they might have published in the past an article on the modelisation of mecanical efforts in rugby.
link: the article, its in french though
+ Show Spoiler +
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Awesome idea. I think positioning, committment and timing are all really important though. Perhaps you could test 3 different tackles (shoulder to legs, shoulder to body, arms to body) for each subject, and try to find people at similar heights with different weights.
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It feels so good to see other people suffering through the hell of IB. Have you had to pull an all-nighter yet? I had one about a month ago. I felt special.
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Thanks for all the feedback guys, I appreciate it a lot.
heyoka: I've had a look at Google Scholar, but most of the physics stuff has to do with injuries :/ I'll keep looking though, thanks for the tip. I haven't combed the school database, and can't right now (because we're on spring break) but I'll look through it soon enough.
Luddite: Yeah I know that definition is a little vague, my advisor and I were talking about rewording that to make it more specific. For effectiveness in the tackle, it should be basically be bringing the guy down as quickly as possible, and possibly driving him back a few metres while doing it. I'm not sure if my proposed experiment tests that very well though :/. I guess I can just define the "effectiveness" as the maximum transfer of momentum or kinetic energy, because those two factors combined should be enough to determine whether a tackle will be successful or not. I'm not including tackling technique here (yeah I know, it's a significant omission) because it will be too difficult to get different subjects to tackle exactly the same way. If the results are inconclusive, I might think about testing it.
micronesia: All the trials will be almost risk-free, as the guys will only be hitting tackle bags. For the theoretical approach, I really don't understand how the two equations are that different (hehehe). Can you enlighten me?
FaCE_1: Can you remember any more specific details? This is exactly the kind of stuff that I'm looking for. If you can that would be seriously awesome
Bebop Berserker: Yes, I am guilty of skipping the hypothesis  . In terms of the actual mathematical relationships I'm not too worried about it, I'm really just focused on getting the raw data first, but that's definitely an obstacle I'll have to tackle later on. Thanks for the advice.
canucks12: According to the kinetic energy equation, that is what should happen, but I'm not entirely sure that will translate perfectly under real-life conditions. Hopefully the data will fall in line with that assumption, but we never know :/. The mass of the "defender" will be a constant, as the same tackle bag will be used each time.
Yeah Physics EEs are hard, my school (which has been doing IB for over 25 years) has never had a single student get an A. Kudos to your friend for that.
Groslouser: Yeah the position thing was one of the first "lack of controls" that sprung to mind...I decided to ignore it for a while and focus on getting the data. I'll be testing subjects of all sizes, big forwards and small backs, so the range of data will be pretty diverse. If I decide that I need to focus on a specific position, it'll probably be scrum-half, because that's what I play . The trouble with dealing with players in general is that certain positions (like the scrum-half) are expected to be small, while others (props) are expected to be big, so generalizations about velocity and mass in general are hard to apply to both simultaneously. However, this question is specifically dealing with changes in mass and velocity, not existing values, so that might be a way around that. Thanks for the article, I'll research on the engineers as soon as I get time.
sc4k: That was originally what my experiment was trying to test, but I decided that it was too difficult to test, as it relied really heavily on the technique used. If I have space left in the essay, I'll definitely come back to that.
rockon1215: Never had an all-nighter yet, my worst was 3AM. I think it's because I'm not personally motivated enough, haha. I'd rather take the hit to my grades than stay up and have to suffer through school the next day.
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United States24701 Posts
On March 26 2010 15:32 aev wrote:
micronesia: All the trials will be almost risk-free, as the guys will only be hitting tackle bags. For the theoretical approach, I really don't understand how the two equations are that different (hehehe). Can you enlighten me?
Not sure if me telling you this is 'cheating' or not but here's an explanation:
+ Show Spoiler +
According to the momentum equation p=mv, you can get more momentum (better for pushing other things in a collision) by increasing mass or velocity. If you double mass, you double momentum. If you double velocity, you double momentum. Mass and velocity contribute equally towards the momentum.
Kinetic energy however does not work this way. The formula is KE = 1/2 m v^2. If you double the mass you double the KE, but if you double v you quadruple the KE. Therefore increasing velocity has a greater affect on KE than increasing mass would.
However, a collision between two football players is probably inelastic meaning momentum is conserved during the collision but energy is not....
There's some food for thought?
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I understand why increasing velocity results in a greater growth of kinetic energy than the linear growth of momentum (that's really just math), but what I guess I should have asked about is the difference between the two concepts. What exactly is the difference between momentum and kinetic energy? Does high momentum or high kinetic energy make a rugby player more difficult to stop? Again, I'd probably ask my advisor, but we're on break :/. Any help would be great
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Wow, that's a pretty interesting, though not unheard of EE topic. I also did an EE in physics, though a different one. Initially I considered a similar topic on billiard ball collisions and rotations, but I found it too much of a hassle to measure and quantify, so I just did a simple experiment with lab stuff  (got an A though ;o).
You should really think hard about the topic, giving away the answer here would kill your investigation, because it's an actually interesting thing to think about. Maybe you could talk about it in your essay? As long as your answer is justified by pretty plots, graphs, and some independent conceptual thinking, everything is okay with your EE.
Also, I cannot stress enough the importance of the way your EE looks like. Pretty (and plenty of) graphs (in appendices if you feel like it), figures, pictures, good formatting and referencing make your things look much much better. Look at model EEs online if you want to see what they grade high.
Aanyway, good luck with it, and enjoy your IB! It's not actually too bad, the only times I stayed up late I was watching VODs/movies/anime/reading manga ^^
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Wait a sec, shouldn't EEs be due sometime really soon.
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p=mv.... conservation of momentum. It doesn't matter which one lol. kinetic energy isn't preserved so you can forget 0.5mv^2
furthermore the impulse force is delta p
I'd say the real thing to study is how fast a 30kg man can run compared to a 35kg man.
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It's obviously velocity because higher velocity gives the opponent less time to react. :-P
While I wasn't really serious about that, I still think that velocity is the way to go. Anyway this is a pretty interesting question, let us know how it goes.
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CA10828 Posts
hehe i did my EE in history. easiest thing ever...
...except for the research. i had to search through over 5 libraries in my area (including universities!) to find relevant books on my topic. i ended up finding a few good sources at some law school library an hour away from my house.
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I don't think the research question is very good. "More beneficial" in increasing "effectiveness". Increasing velocity and increasing mass both increase "effectiveness," so what's the problem here? It's not like, 10 pounds of more mass = 5 more m/s so we have to find a maximum balance...
I'm not good at explaining, but I hope you understand my concern. GL
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So...I am totally about to mooch off of your post, because its amazing how many people have ideas for your EE topic, and mine is physics/sports related to.
Soooo
For mine I am posing the question of "Which is more efficent in basketball freethrows, a underhand (granny) shot, or a regular overhead shot"
I know I am going to do an experiment like yours with the camcorder and stuff, but i have no clue on how to go about doing calculations or anything.
Does anyone have ideas?
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CA10828 Posts
On April 01 2010 09:43 WoWz3rZ wrote:So...I am totally about to mooch off of your post, because its amazing how many people have ideas for your EE topic, and mine is physics/sports related to. Soooo For mine I am posing the question of "Which is more efficent in basketball freethrows, a underhand (granny) shot, or a regular overhead shot" I know I am going to do an experiment like yours with the camcorder and stuff, but i have no clue on how to go about doing calculations or anything. Does anyone have ideas?
what is your definition of efficient?
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actually I think mass would make you a better tackler. let me explain.
a higher mass helps you stay upright. for most tackles both people go down, but keeping your balance depends more on your delta v than your delta p. if you have a 100 pound person going from 4 m/s to 0 or a 200 pound person going from 2 m/s to 0, the first guy is going to have a harder time staying standing simply because it's harder to get your legs in the right position if you're moving faster. also, in an inelastic collision the two bodies end up moving with the center of mass of the system; if you're bigger the system center of mass is going to be closer to your center of mass so you suffer less of a velocity change. i don't know about rugby, but in football it is advantageous to push the guy back if you can as well as taking him down, and it's a lot easier if you're bigger and still standing (plus as a bigger person you are probably stronger)
secondly KE is dissipated in an inelastic collision, and it has to go somewhere - heat and sound, but it is also dissipated into your body through vibrations and such. this means if you're a light, fast tackler, every time you tackle someone you're taking a pretty big beating. yes, some of the energy is dissipated into them, but you don't tackle the same person every time.
also, from a practical perspective, it's harder to increase speed. you can find people who weigh 1.5x as much as you, but there are much less people that can run 1.5x as fast, since all rugby players train to be fast.
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EPT
