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Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: missbeautiful789 on November 03, 2010, 04:27:05 pm

Title: Physics prac tommorow..uncertain abot uncertainties.
Post by: missbeautiful789 on November 03, 2010, 04:27:05 pm
Quick question..... What do we use for reaction time?

and

Say we have a pendulum..... In two readings if found the time taken for 20 osc was 50.45 and 55.56 seconds.

what is the time taken for 1 period and what is the uncertainty. ???
Title: Re: Physics prac tommorow..uncertain abot uncertainties.
Post by: Deadly_king on November 03, 2010, 05:15:50 pm
Quote from: Salahuddin_Ansari on November 03, 2010, 04:27:05 pm
Quick question..... What do we use for reaction time?

and

Say we have a pendulum..... In two readings if found the time taken for 20 osc was 50.45 and 55.56 seconds.

what is the time taken for 1 period and what is the uncertainty. ???

Reaction time : 0.2s

You should use the columns in your table to insert  t1, t2, mean time<t> and then periodic time(T)

N=20
t1= 50.45s    t2= 55.56s

Hence mean time <t>= (50.45 + 55.56)/2 = 53.01s

Periodic time =  53.01/20 = 2.651s

Uncertainty is the reaction time, since the stopwatch used measured values upto 4sf which makes an uncertainty of 0.01 which is negligible when compared to 0.2s of reaction time. ;)

% uncertainty = 0.2/2.651 * 100 = 7.5%

Hope it helps :)
Title: Re: Physics prac tommorow..uncertain abot uncertainties.
Post by: missbeautiful789 on November 03, 2010, 05:21:25 pm
I owe you 2 +reps DK, but I'm finding it difficult to spread the love.

Thanks, you're incredibly helpfull
Title: Re: Physics prac tommorow..uncertain abot uncertainties.
Post by: Deadly_king on November 03, 2010, 05:30:50 pm
Quote from: Salahuddin_Ansari on November 03, 2010, 05:21:25 pm
I owe you 2 +reps DK, but I'm finding it difficult to spread the love.

Thanks, you're incredibly helpfull

Spread the love = +rep another member before +repping this one ;)

Don't worry about it. Am just glad of being able to clear your doubt before the exams.

Am having practicals tomorrow as well :D
Title: Re: Physics prac tommorow..uncertain abot uncertainties.
Post by: Dania on November 03, 2010, 07:13:59 pm
Hi. For the May/June 2010 Paper 32. The second question is on magnets. What would the uncertainty/limitations and improvements be for the experiment?

Paper attached below.
Title: Re: Physics prac tommorow..uncertain abot uncertainties.
Post by: Deadly_king on November 05, 2010, 06:29:57 am
Quote from: Dania on November 03, 2010, 07:13:59 pm
Hi. For the May/June 2010 Paper 32. The second question is on magnets. What would the uncertainty/limitations and improvements be for the experiment?

Paper attached below.

I guess you'll get all the possibilities from the marking schemes.

Here (http://www.xtremepapers.net/CIE/International%20A%20And%20AS%20Level/9702%20-%20Physics/9702_s10_ms_32.pdf)