• Log InLog In
  • Register
Liquid`
Team Liquid Liquipedia
EST 09:09
CET 15:09
KST 23:09
  • Home
  • Forum
  • Calendar
  • Streams
  • Liquipedia
  • Features
  • Store
  • EPT
  • TL+
  • StarCraft 2
  • Brood War
  • Smash
  • Heroes
  • Counter-Strike
  • Overwatch
  • Liquibet
  • Fantasy StarCraft
  • TLPD
  • StarCraft 2
  • Brood War
  • Blogs
Forum Sidebar
Events/Features
News
Featured News
RSL Revival - 2025 Season Finals Preview8RSL Season 3 - Playoffs Preview0RSL Season 3 - RO16 Groups C & D Preview0RSL Season 3 - RO16 Groups A & B Preview2TL.net Map Contest #21: Winners12
Community News
ComeBackTV's documentary on Byun's Career !3Weekly Cups (Dec 8-14): MaxPax, Clem, Cure win3Weekly Cups (Dec 1-7): Clem doubles, Solar gets over the hump1Weekly Cups (Nov 24-30): MaxPax, Clem, herO win2BGE Stara Zagora 2026 announced15
StarCraft 2
General
Did they add GM to 2v2? Weekly Cups (Dec 8-14): MaxPax, Clem, Cure win ComeBackTV's documentary on Byun's Career ! RSL Revival - 2025 Season Finals Preview Weekly Cups (Dec 1-7): Clem doubles, Solar gets over the hump
Tourneys
RSL Offline Finals Info - Dec 13 and 14! Master Swan Open (Global Bronze-Master 2) Winter Warp Gate Amateur Showdown #1: Sparkling Tuna Cup - Weekly Open Tournament $5,000+ WardiTV 2025 Championship
Strategy
Custom Maps
Map Editor closed ?
External Content
Mutation # 504 Retribution Mutation # 503 Fowl Play Mutation # 502 Negative Reinforcement Mutation # 501 Price of Progress
Brood War
General
FlaSh on: Biggest Problem With SnOw's Playstyle How Rain Became ProGamer in Just 3 Months BGH Auto Balance -> http://bghmmr.eu/ [BSL21] RO8 Bracket & Prediction Contest BW General Discussion
Tourneys
[Megathread] Daily Proleagues [BSL21] WB SEMIFINALS - Saturday 21:00 CET [BSL21] RO8 - Day 2 - Sunday 21:00 CET [ASL20] Grand Finals
Strategy
Game Theory for Starcraft Current Meta Simple Questions, Simple Answers Fighting Spirit mining rates
Other Games
General Games
Stormgate/Frost Giant Megathread Path of Exile General RTS Discussion Thread Dawn of War IV Nintendo Switch Thread
Dota 2
Official 'what is Dota anymore' discussion
League of Legends
Heroes of the Storm
Simple Questions, Simple Answers Heroes of the Storm 2.0
Hearthstone
Deck construction bug Heroes of StarCraft mini-set
TL Mafia
Mafia Game Mode Feedback/Ideas Survivor II: The Amazon Sengoku Mafia TL Mafia Community Thread
Community
General
US Politics Mega-thread Things Aren’t Peaceful in Palestine The Games Industry And ATVI Russo-Ukrainian War Thread YouTube Thread
Fan Clubs
White-Ra Fan Club
Media & Entertainment
Anime Discussion Thread [Manga] One Piece Movie Discussion!
Sports
2024 - 2026 Football Thread Formula 1 Discussion
World Cup 2022
Tech Support
Computer Build, Upgrade & Buying Resource Thread
TL Community
TL+ Announced Where to ask questions and add stream?
Blogs
The (Hidden) Drug Problem in…
TrAiDoS
I decided to write a webnov…
DjKniteX
James Bond movies ranking - pa…
Topin
Thanks for the RSL
Hildegard
Customize Sidebar...

Website Feedback

Closed Threads



Active: 1265 users

Study Blog Part 3: Center of mass

Blogs > Mr.X546
Post a Reply
Zhazulo
Profile Blog Joined February 2011
Sweden226 Posts
February 03 2013 20:27 GMT
#1
Hey all!

This week will be a rather short blog. I've had plenty to do (trying out new study habits, playing SC2, and else) but I wrote together a bit of the week!

Code S has really occupied me daily, hehe. With it being on at 10:10 AM more or less every day and our school having WiFi in every building, it's a bit too easy to tune in ^^ oh well!

I'll be playing at UniSL FInals next week. You know, the guys who made the "Land of the Zerg" video. I believe I'll be playing first on Saturday at 1 pm. Be sure to tune in then!

1) What have you done this week?

+ Show Spoiler +
i) Topics covered

Center of mass

ii) Time spent/what sessions?

Theory reading (1 x 2h)

4 calculation sessions (4 x 2h)

Repetition (~2 h)

Total=12 h

iii) Topics explained

I was supposed to go through free body diagrams in 2D as well, but there was a lot to do with just center of mass, so I ended up doing only that. Luckily, next week is only about FBDs and I managed to read the theory about FBDs in 2D, so I think it will be ok in the end.

Center of mass is about calculating the center of mass of an object or several objects. This is relevant because mechanics is about simplifying complex situations, and in many cases, objects can be approximated by being a single point object, which would be located at it's center of mass.

Calculations include two areas; finding the center of mass of a system of particles or the center of mass for a body. In this case, we approximate the body to be a rigid body; it will NOT change form (more about that later on!)

Finding the center of mass of a particle system can be done with a straightforward formula; finding the sum of the particles' position vectors, multiplied by their corresponding mass, and then dividing the sum with the total amount of mass of the system.

A more common situation is to find the center of mass of a body. It get's a little trickier, but there are several techniques. Basically, the same principle applies; approximate the body to a particle. If the body is complex, the idea is to divide it into sub-bodies, calculate their center and then add them all up as a particle system.

To find the center of mass of a body (or a sub-body!) we can use Pappus Rule. Pappus rule relates the area or volume of rotation around an axis to the center of mass and the line or area which is to be rotated. The equations are as following:

Volume of rotation=2(pi)*Yg*Area
Area of rotation=2(pi)*Yg*Length

where:
Yg - is the y-coordinate of the center of mass (if the figure is to be rotated around the x-axis)

Most of this theory will become understandable when it comes to solving problems, that's when the learning really happens!

iv) What challenges did you face?
Most of the exercises were tedious and quite daunting to start at, but it got easier and easier the more comfortable I got! The main focal point was just to do calculations


2) Problems/Exercises

+ Show Spoiler +
No exercises this week either maybe I'll have to rethink how I should approach this section, as I have yet to upload a single exercise ^^


3) Reflection Questions
+ Show Spoiler +
How would Pappus Rule be applied if the rotation would only be half-way?

How can Pappus Rule be used to find the area and/or the volume of a figure?


4) For Next week
+ Show Spoiler +
i) What topics? What do you know about this?
Next week will be about free body diagrams, but I discussed this last week, so nothing really new to add here!


Have a week!

ThePhan2m
Profile Blog Joined September 2004
Norway2750 Posts
Last Edited: 2013-02-03 21:58:04
February 03 2013 21:57 GMT
#2
Good job, expecting some exercise pictures next week!!
RoyGBiv_13
Profile Blog Joined August 2010
United States1275 Posts
February 04 2013 18:32 GMT
#3
Sort of related to your blog:

A homework short story:
+ Show Spoiler +
As a freshman at engineering college, I had fast-tracked my way into taking multi-dimensional calculus through AP classes in high school. The calculus professor, Dr. Alden, used the Mathematica-like program, Maple, nearly every day to show us examples of how to do incredibly complicated equations using the school-issued (and tuition bloating) laptops. The brightest students quickly caught on that you could use this program to do your homework. You could just print out the results instead of breaking your wrist writing page after page of equations that you inevitably just plugged into the computer anyway.

There was an extensive library as part of Maple. It could do all sorts of animations, differential equations, symbolic logic and really anything a mathematician or engineer could need. There was even keyboard shortcuts to quickly format the worksheet to make it organized and able to be submitted for homework. Part of the skill in using the program was to learn how to ask questions of it. The help file was accessed by a quick "?<command>".

There was one notorious week, two weeks before the final, where Dr Alden had to teach several topics per day to accommodate the schedule. He would teach one subject during the lecture, then assign another for homework. Naturally, calculating the center of mass was a homework assignment. One not even covered in the textbook. The entire class was confused over the instructions and examples (the topic itself isn't too difficult, but there are a number of tricky things in multivariable land that quickly catch up with you). Only three of us turned in the homework on time.

It was my shortest homework assignment since elementary school. It took me under 3 minutes to complete.

The trick? "?Centerofmass".... Turned out that Maple had a CenterOfMass(f(x,y,z),x=A..B,y=C..D,z=E..F) command. I transcribed the functions into the program, ran the worksheet, and printed it. The average length of that homework (the prof recorded these stats, being a Math prof and all) was 11 pages. He had exclude my 100% homework of 2 pages as an outlier.

Any sufficiently advanced technology is indistinguishable from magic
Please log in or register to reply.
Live Events Refresh
WardiTV 2025
13:00
Playoffs
Solar vs CureLIVE!
herO vs Spirit
Scarlett vs Gerald
Rogue vs Shameless
MaNa vs ShoWTimE
Nice vs Creator
WardiTV994
ComeBackTV 513
TaKeTV 245
IndyStarCraft 142
Rex132
LiquipediaDiscussion
[ Submit Event ]
Live Streams
Refresh
StarCraft 2
Lowko460
IndyStarCraft 142
Rex 132
StarCraft: Brood War
Britney 36164
Sea 4364
Horang2 1252
Larva 911
EffOrt 662
GuemChi 628
Mini 530
Soma 492
Stork 392
Sharp 352
[ Show more ]
ZerO 309
Snow 283
firebathero 276
PianO 234
Last 226
BeSt 207
Hyuk 153
hero 142
Rush 117
JYJ 101
Hyun 100
Killer 90
Light 75
Pusan 71
sorry 54
Mind 52
Sea.KH 48
Mong 48
Aegong 26
soO 22
Movie 22
Terrorterran 20
Shine 15
scan(afreeca) 12
Dota 2
Gorgc5202
singsing3729
qojqva1970
Dendi860
XcaliburYe129
syndereN53
League of Legends
C9.Mang0318
rGuardiaN114
Counter-Strike
x6flipin455
byalli376
allub164
oskar121
Other Games
B2W.Neo1325
olofmeister1139
Beastyqt587
crisheroes391
Hui .254
ArmadaUGS74
QueenE71
Livibee62
Mew2King59
Trikslyr27
ZerO(Twitch)10
nookyyy 7
Organizations
StarCraft: Brood War
lovetv 7
StarCraft 2
Blizzard YouTube
StarCraft: Brood War
BSLTrovo
sctven
[ Show 12 non-featured ]
StarCraft 2
• AfreecaTV YouTube
• intothetv
• Kozan
• IndyKCrew
• LaughNgamezSOOP
• Migwel
• sooper7s
StarCraft: Brood War
• BSLYoutube
• STPLYoutube
• ZZZeroYoutube
Dota 2
• WagamamaTV437
League of Legends
• Nemesis1758
Upcoming Events
WardiTV 2025
20h 51m
ByuN vs TBD
Clem vs TBD
OSC
23h 51m
CranKy Ducklings
1d 19h
WardiTV 2025
1d 20h
SC Evo League
1d 22h
Ladder Legends
2 days
BSL 21
2 days
Sziky vs Dewalt
eOnzErG vs Cross
Sparkling Tuna Cup
2 days
Ladder Legends
3 days
BSL 21
3 days
StRyKeR vs TBD
Bonyth vs TBD
[ Show More ]
Replay Cast
3 days
Wardi Open
3 days
Monday Night Weeklies
4 days
WardiTV Invitational
5 days
Replay Cast
6 days
WardiTV Invitational
6 days
ByuN vs Solar
Clem vs Classic
Cure vs herO
Reynor vs MaxPax
Liquipedia Results

Completed

Acropolis #4 - TS3
RSL Offline Finals
Kuram Kup

Ongoing

C-Race Season 1
IPSL Winter 2025-26
KCM Race Survival 2025 Season 4
YSL S2
BSL Season 21
Slon Tour Season 2
CSL Season 19: Qualifier 1
WardiTV 2025
META Madness #9
eXTREMESLAND 2025
SL Budapest Major 2025
ESL Impact League Season 8
BLAST Rivals Fall 2025
IEM Chengdu 2025
PGL Masters Bucharest 2025
Thunderpick World Champ.
CS Asia Championships 2025
ESL Pro League S22

Upcoming

CSL Season 19: Qualifier 2
CSL 2025 WINTER (S19)
BSL 21 Non-Korean Championship
Acropolis #4
IPSL Spring 2026
Bellum Gens Elite Stara Zagora 2026
HSC XXVIII
Big Gabe Cup #3
OSC Championship Season 13
ESL Pro League Season 23
PGL Cluj-Napoca 2026
IEM Kraków 2026
BLAST Bounty Winter 2026
BLAST Bounty Winter Qual
TLPD

1. ByuN
2. TY
3. Dark
4. Solar
5. Stats
6. Nerchio
7. sOs
8. soO
9. INnoVation
10. Elazer
1. Rain
2. Flash
3. EffOrt
4. Last
5. Bisu
6. Soulkey
7. Mini
8. Sharp
Sidebar Settings...

Advertising | Privacy Policy | Terms Of Use | Contact Us

Original banner artwork: Jim Warren
The contents of this webpage are copyright © 2025 TLnet. All Rights Reserved.