Author Topic: physics help needed........plz  (Read 4951 times)

Offline ashwinkandel

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Re: physics help needed........plz
« Reply #15 on: October 02, 2010, 06:13:22 pm »
6 significant figures. You ignore the last 0.
Usually its to 3.
ending zero after decimal point is significant , isn't it?

Offline iluvme

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Re: physics help needed........plz
« Reply #16 on: October 02, 2010, 06:38:17 pm »
You mean the last zero?
Yes.
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Offline ashwinkandel

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Re: physics help needed........plz
« Reply #17 on: October 02, 2010, 06:56:10 pm »
if the last digit was significant then why did u say 6 s.f. there should have been 7 isn't it? and you have said ignore last 0. how can we ignore it if it is significant?

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Re: physics help needed........plz
« Reply #18 on: October 02, 2010, 07:03:31 pm »
if the last digit was significant then why did u say 6 s.f. there should have been 7 isn't it? and you have said ignore last 0. how can we ignore it if it is significant?

Damn.My mistake, No it is not significant. Sorry.
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Offline Deadly_king

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Re: physics help needed........plz
« Reply #19 on: October 03, 2010, 05:16:56 am »
Damn.My mistake, No it is not significant. Sorry.
Nope......ashwin is right there. Indeed the number is correct to 7 sf.

Since the zero has been written and is after decimal point, it is certainly significant.

Otherwise the last zero would not have been written to form a number correct to 6 sf.

I apologise for my mistake :)

Example : Express 1.99 correct to 2sf ----> 2.0

The zero counts as a significant figure.

I had already stated this example before  :P
« Last Edit: October 03, 2010, 09:01:44 am by Deadly_king »

Offline ashwinkandel

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Re: physics help needed........plz
« Reply #20 on: October 03, 2010, 01:26:51 pm »
one more question related to this:
5 A student makes measurements from which she calculates the speed of sound as 327.66ms–1.
She estimates that her result is accurate to ±3 %.
Which of the following gives her result expressed to the appropriate number of significant figures?
A 327.7ms–1 B 328ms–1 C 330ms–1 D 300ms–1

elemis

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Re: physics help needed........plz
« Reply #21 on: October 03, 2010, 01:38:28 pm »
Is it D ?

Which year ?

Offline ashwinkandel

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Re: physics help needed........plz
« Reply #22 on: October 03, 2010, 01:54:04 pm »
ya it is D . Can you explain me how is it D?

elemis

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Re: physics help needed........plz
« Reply #23 on: October 03, 2010, 01:56:21 pm »
ya it is D . Can you explain me how is it D?

I THINK this is the explanation :

Since the uncertainty is given to a maximum of 1 s.f. therefore the actual answer should also be given to an accuracy of 1 SF.

Hence, answer = D

What year is this question from ?


Offline ashwinkandel

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Re: physics help needed........plz
« Reply #24 on: October 03, 2010, 02:12:02 pm »
thanks for the explanation. this question was from CIE 2003 May/June paper 1.

elemis

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Re: physics help needed........plz
« Reply #25 on: October 03, 2010, 02:30:42 pm »
Dude, the MS says the answer is C ::)

How could say I was correct ? My answer and explanation is wrong.

Offline ashwinkandel

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Re: physics help needed........plz
« Reply #26 on: October 03, 2010, 02:38:07 pm »
ohh i m really sorry. i apolologise for this i mistakely looked another marking scheme.

elemis

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Re: physics help needed........plz
« Reply #27 on: October 03, 2010, 02:39:20 pm »
ohh i m really sorry. i apolologise for this i mistakely looked another marking scheme.

I'll be honest too... I really dont know how its C :P

Offline Deadly_king

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Re: physics help needed........plz
« Reply #28 on: October 04, 2010, 05:31:41 am »
one more question related to this:
5 A student makes measurements from which she calculates the speed of sound as 327.66ms–1.
She estimates that her result is accurate to ±3 %.
Which of the following gives her result expressed to the appropriate number of significant figures?
A 327.7ms–1 B 328ms–1 C 330ms–1 D 300ms–1

Let delta C = c where C is the speed of sound.

% uncertainty = c/C * 100
                 3 = c/327.66 * 100 ---> c = 9.8

But c is taken as 10 since the % uncertainty (3%) is given correct to 1 significant figure.

Therefore the correct answer should be to the nearest tenth which results in C = 330 m/s

Hope you understood what I am trying to say :)



Offline ashwinkandel

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Re: physics help needed........plz
« Reply #29 on: October 04, 2010, 12:50:11 pm »
you are great deadly_king. thanks again .