ReCom.org
Portal Page Forum Wiki Social Groups Scholarship Holders Infobase Site Map About
Go Back   ReCom.org > Forum > ReCom Cafe > Education > SPM & STPM

SPM & STPM Post questions on SPM and STPM topics ONLY.

STPM Phycis [Help]

Reply
 
Thread Tools
Sola Male
Super Junior Member
 
Sola's Avatar
 
Join Date: Mar 2010
Posts: 11
  #1 Old 30-09-2010 Default STPM Phycis [Help]

I'm very confused.
Suppose,question 1(a),i get the asnwer:
x=1.3456
=1.35(correct to 3 sf)

Then,for 1(b),it requires me to substitute the answer from 1(a),which should i choose?1.3456 or 1.35?

I hope there is some reliable answer(preferable refer to previous STPM answer scheme).I cant get any confirmed(trusted) answer from my teacher(s) or friends from other school.
Sola is offline   Reply With Quote
henry_yew Male
The Iron Boot
ReMag Writer
Forum Moderator
 
henry_yew's Avatar
 
Join Date: Jun 2006
Posts: 1,567
  #2 Old 01-10-2010 Default Re: STPM Phycis [Help]

Quote:
Originally Posted by Sola View Post
I'm very confused.
Suppose,question 1(a),i get the asnwer:
x=1.3456
=1.35(correct to 3 sf)

Then,for 1(b),it requires me to substitute the answer from 1(a),which should i choose?1.3456 or 1.35?

I hope there is some reliable answer(preferable refer to previous STPM answer scheme).I cant get any confirmed(trusted) answer from my teacher(s) or friends from other school.
Personally, I would use 1.3456 instead of 1.35 to substitute into any calculation in part 1(b). Then, whatever answer I get for part 1(b) I can write it in three significant figures, if that is what the question wants.

The reason to use 1.3456 instead of 1.35 is that the final answer for 1(b) may be different if you use three significant figures for your calculation instead of four.

It is never a mistake to use more decimal places in your calculations for a more accurate final answer. Using the rounded off figure for your future calculations can bring about errors that will only get worse if there are more calculations that follow. The error that originates from the rounding off will be carried forward to the next calculation, and if you round off the next answer and it is to be used in another set of calculations, that error will be even greater.

Take for example, I have a big mass of 6000 kg acting on a square plate of 1.25 metres. (a) Calculate the force acting on the square plate and report the answer in 2 significant figures. (b) Calculate the axial stress experienced by the square plate and report the answer in 3 significant figures.

The axial stress can be defined as the force acting on the square plate divided by the area of the square plate.

(a) Force = 6000 kg x 9.81 m/s^2 = 58860 N (report as 59000 N or 59 kN)

(b) Stress = Force / Area = 58860 N / (1.25 x 1.25) m^2 = 37670.4 Pa (report as 37700 Pa or 37.7 kPa)

If you had used the answer in part (a), that is 59 kN, and substitute that in part (b), you would have got 37.8 kPa, and not 37.7 kPa. The difference here may seem small, but imagine that you will use the answer in part (b) for perhaps part (c) or part (d) in your exams. Also, some teachers might even mark you wrong for writing 37.8 kPa instead of 37.7 kPa.

Therefore, play safe. The final answer counts, so it's better not to use rounded off figures for future calculations. In engineering practice, especially, it's considered bad practice to use rounded off figures for future calculations. Sometimes, the difference by one-hundredth of a millimetre counts.
__________________
[]

Last edited by henry_yew; 01-10-2010 at 01:50 AM.
henry_yew is offline   Reply With Quote
The Following User Says Thank You to henry_yew For This Useful Post:
Sola Male
Super Junior Member
 
Sola's Avatar
 
Join Date: Mar 2010
Posts: 11
  #3 Old 06-10-2010 Default Re: STPM Phycis [Help]

Thx for your reply,appreciate it^^
Sola is offline   Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
[STPM] STPM 2007 students.. Let's trade our trial papers HERE..!! CLY SPM & STPM 36 27-10-2007 08:38 AM
[STPM] Analysis and summary of trial STPM 2007:Biology 4seasonspring SPM & STPM 4 24-10-2007 07:09 PM
[STPM] 2007 Malacca stpm trial exam biology paper 2 sven_ SPM & STPM 0 24-10-2007 11:55 AM
[STPM] Analysis and summary of trial STPM 2007:Pengajian Am 4seasonspring SPM & STPM 11 23-10-2007 06:57 PM
[STPM] correction in trial stpm question paper cyclic SPM & STPM 2 05-10-2007 07:37 PM


All times are GMT +8. The time now is 10:23 PM.


Powered by vBulletin® Version 3.7.6
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

ReCom stands for Reborn Community. It has no affiliation with other organizations that may share the same name. The views expressed in this website solely represent the authors point of view and do not necessarily reflect the views of ReCom Anchors and other ReCom users.


 

Page generated in 0.08272 seconds with 15 queries