what is the point of revising now?

• anpanman

  4 Jul 09, 11:27

  Originally posted by eagle:

  Let's try this simple O levels questions

   

  

  A non-uniform plank weighing 300N is set up as shown. The spring balance reads 160 N when the small boy stands at A, and 760 N when the small boy stands at B.

   

  a) State what is meant by moment of a force.

  b) Calculate the weight of the boy.

   

   

  Can do part b then you can take your time to revise

  May I ask whether the spring balance here measures the resultant force or it exerts a force or anything like that?

  Thanks.(I suppose it is the former)

• yiha093

  4 Jul 09, 11:52

  balance is tension i believe?  so its exerting an upward force.

• eagle

  4 Jul 09, 11:53

  Originally posted by anpanman:

  May I ask whether the spring balance here measures the resultant force or it exerts a force or anything like that?

  Thanks.(I suppose it is the former)

  Resultant force of the whole system is zero

• eagle

  4 Jul 09, 11:57

  Originally posted by yiha093:

  moment of balance in 1st case = 160x5=800

  moment of balance in 2nd case= 760x5=3800

  difference in moment =3000

  after boy moves 10m> diff in N of balance= 760-160=600N 

  can assume so ?  =x

  need to find D of pivot to cg of rule right?

  still doing=x 1st time doing this kind of qn -.-

  so in the end my ans is 600N

  *did qn assuming setup in equilibrium

  i guess im wrong >_< * i feel so excited at the prospect of learning how to do ~ ! enlighten me =X

  It's 300 N

  Note that the c.g. is not at the centre of the plank because it is non-uniform

   

  Btw, this is a question I put on ExamWorld ;)

• yiha093

  4 Jul 09, 12:12

  Originally posted by eagle:

  It's 300 N

  Note that the c.g. is not at the centre of the plank because it is non-uniform

   

  Btw, this is a question I put on ExamWorld ;)

  yaya i noe the c.g not at centre

  if not much much easier ler.

  haha so ans is 300N ?

• yiha093

  4 Jul 09, 13:55

  erm. btw i dun understand this

   

  Sub (1) into (2):
  800 + 2W + 8W = 3800
  10W = 3000
  W = 300

• eagle

  4 Jul 09, 14:40

  Originally posted by yiha093:

  erm. btw i dun understand this

   

  Sub (1) into (2):
  800 + 2W + 8W = 3800
  10W = 3000
  W = 300

  solving simultaneous equations

• mlmersrlosers

  4 Jul 09, 15:16

  know urself...an average person he will forget after 3 days.

• eagle

  4 Jul 09, 18:47

  Originally posted by mlmersrlosers:

  know urself...an average person he will forget after 3 days.

  hmmm

  then I must be lucky to have so many above average students...

   

   

  Just kidding... The most important is understanding plus drilling in the understanding... It's not about drilling questions, but the understanding of it :D

• yiha093

  4 Jul 09, 19:42

  er. got more so called physics method of solving ?

  no use sim ?

  can show ?  cause my train of thought is using phy method de..?

• yiha093

  4 Jul 09, 19:43

  Originally posted by mlmersrlosers:

  know urself...an average person he will forget after 3 days.

  i disagree? maybe its just u thts forgetful ? -.-

• Lee012lee

  4 Jul 09, 20:08

  There are students who need no revision at all.

  There are students who just understand the formula and concepts and they can solve the questions.

  There are students who pay attention in class only and they can remember all the facts taught in class and use the facts to answer the questions in the exam.

  If you are one of these students, no revision is needed at all.

  For other students, it is advisable that they should revise as frequently as possible as research has shown that human being's memory tend to fall as time passes and the memory needs to be re-charged constantly.

  In addition, a revision does not mean only going through all the formula, concepts and facts. A revision involves the application of the formula, concepts and facts to solve and answer the different types of examination questions. There is also room for improvement in your answers in terms of presentation of the answers, solving methods and answering skills, ability to solve and answer the questions in shorter and shorter time.

  So, it is advisable to revise as frequently as possible ie do not wait until the last minute to hold the Buddha's legs.

• cassie

  4 Jul 09, 20:09

  Can i confess...i left most of my school work back in school! Ok, minus the maths bit which occasionally pops into use when i build the excel models. LOL!
• eagle

  4 Jul 09, 20:15

  Originally posted by yiha093:

  er. got more so called physics method of solving ?

  no use sim ?

  can show ?  cause my train of thought is using phy method de..?

  the physics of questions is to understand the concepts involved and come out with the right equations

  after that it is all maths ;)

  In this question, the physics is to understand that it is about principles of moments, about c.g. that's not at the centre..... and to come out and use the equations on moments...

  Then it's maths :D

• yiha093

  4 Jul 09, 21:44

  nooooooooooooooooooooooooooooo

  i suck at maths

  so i naturally suck at phy turn into maths thingy -.-''

  didnt even occur to me of using sim eqns cause everything cher give is like test what u know in PHYSICS. not maths ._.

  eeee. z.z

• yiha093

  4 Jul 09, 21:45

  Originally posted by eagle:

  the physics of questions is to understand the concepts involved and come out with the right equations

  after that it is all maths ;)

  In this question, the physics is to understand that it is about principles of moments, about c.g. that's not at the centre..... and to come out and use the equations on moments...

  Then it's maths :D

  looking at the bright side. at least i noe c.g that's not at the centre? -.-

  so can revise later right ! =x LOL

• cassie

  4 Jul 09, 21:50

  Revise now la
• eagle

  4 Jul 09, 21:57

  Originally posted by yiha093:

  nooooooooooooooooooooooooooooo

  i suck at maths

  so i naturally suck at phy turn into maths thingy -.-''

  didnt even occur to me of using sim eqns cause everything cher give is like test what u know in PHYSICS. not maths ._.

  eeee. z.z

  question is taken from a xin min tutorial from an ex student

• eagle

  4 Jul 09, 21:57

  Originally posted by yiha093:

  looking at the bright side. at least i noe c.g that's not at the centre? -.-

  so can revise later right ! =x LOL

  i give u a job

  help me verify that the solutions on examworld are correct ok? :D

• yiha093

  4 Jul 09, 22:19

  Originally posted by eagle:

  i give u a job

  help me verify that the solutions on examworld are correct ok? :D

  dunid check also know sure correct la.... LOL.

• yiha093

  13 Jul 09, 22:28

  sorry for reviving this dead thread. -.-''

  cause i still dont see why must revise now.

  even my teacher is outalked by me and my fren -.-''

• FirePig

  13 Jul 09, 22:31

  dont need to revise.

  Can means can. Cannot means cannot.

• wee_ws

  13 Jul 09, 23:02

  Hi,

    In Singapore education system, 'cannot' must also be made to become 'can' leh :P

    Otherwise, teachers cannot meet KPI (key performance indicator) for value-added results.

  Cheers,
  Wen Shih

• dkcx

  14 Jul 09, 00:14

  Originally posted by yiha093:

  sorry for reviving this dead thread. -.-''

  cause i still dont see why must revise now.

  even my teacher is outalked by me and my fren -.-''

  Must u be this way...

• FirePig

  14 Jul 09, 00:18

  Dont need to help your teacher meet their quota.