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Physics Help HERE ONLY !!
Shogun:
--- Quote from: IGSTUDENT on June 03, 2009, 10:21:26 am ---
--- Quote from: Shogun on June 03, 2009, 10:18:33 am ---
--- Quote from: idol2009 on June 03, 2009, 10:12:39 am ---Since no one answered my question before, i will repost it =)
Hey, I was doing the Oct/Nov 08 Paper 3, and on question 5c), it asks you to calculate the specific latent hear of fusion of ice from the results they have given you...
I usually find this pretty straightforward, but on this problem I was kind of stuck, because my answer didn't match the mark scheme...
The question goes as follows:
"Using a 40W heater, 16.3 g of ice is melted in 2.0 minutes. The heater is then switched off. In a further 2.0 minutes, 2.1 g of ice is melted.
Calculate the specific latent heat of fusion of ice from these results."
So I basically did the following calculation:
Total Energy supplied = 40 x 120 = 4800 J
Total Mass melted by heater = 16.3 g
Specific latent heat = 4800/16.3 = 294.5 J/g
I don't understand what I've done wrong, and what the switching the heater off and the further 2 mins has to do with it?
Any help would be appreciated thanks!
--- End quote ---
oh sorry for u answer to be delayed, so ill try to help u out right away.. ;D
--- End quote ---
SHOGUN
R u a student or a teacher? U seem to have an answer for every problem.And time to solve every query 8)
--- End quote ---
lol im no teacher im a student and i take ig subject its just tht physics is my subject and if i learn something new, id go deep into it even though it was to be studied by students in the universeties.. i daily go to my phsyics to leran something thts out of the syllabus.. ;D
i live in bahrain, and i take exams from cie in ma school.
Ghost Of Highbury:
heat received = mass * temp changed * c
40W --> 40 J/s for 180 seconds = 7200J
7200 = 250 * 5.9 * c
7200/ 1475 = 4.88
ans = 4.88 J/g degree celcius
oct/noc 2008 second variant 5c
Ibiza279:
adi...\m/
they r askin fer the latent heat not the specific latent heat of water
so u just use the equation E=ml
n somebody give me the answer to this question from the answer sheet cause i think the mass v hav to use is 2.1 g n not 16.3g "Using a 40W heater, 16.3 g of ice is melted in 2.0 minutes. The heater is then switched off. In a further 2.0 minutes, 2.1 g of ice is melted.
Calculate the specific latent heat of fusion of ice from these results."
Shogun:
allright, see u have taken the whole mass not the mass of ice which is actually bieng melted, so its not 16.3
u need the mass taken for the ice to melt completely, ie. initial mass of ice melted is 16.3, final mass of ice melted is 2.1... so to get the actuall mass tht was melted u have to subtract
i.e 16.3-2.1=14.2g
then use the formula P x t= mlf
40 x 120 = 14.2 x m (we need to find m)
then sunsitute the equation to : (40 x 120) / 14.2
u get 338j/g which will be ure "M",
do check the mark scheme if its correct....
Shogun:
yup my ans is correct, i hpe i helped , hope u understood... :D
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