IGCSE PHYSICS

[cooldude]

okay guys...another one...
A mercury thread of a thermometer is 12mm long when placed in melting ice, and 82mm long when placed in boiling water.
Find the:
a)length of the thread at 50^oC
b)temperature when the length is 61mm long


plss guys, i need a full-fledged explanation for this cuz whenever i see this type of question after say 2-3 days, i tend to again do it wrong....plsss tell me a way to remember it forever....
Thanks guys!!

look adi we knw that b/w 12mm and 82mm lies 100^.c. cuz melting point of ice=0 and boiling point of water=100. therefore in this scale 1mm=(82-12)/100
=>7/10=0.7
=>1^.c=0.7mm
therfore at 50^.c length=12+(0.7*50)=47mm
and then the next part=>
1^.c=0.7mm
therefore the length for which there is a temperature change=>61-12=49mm
therfore the temperature at this=>49/0.7=70^.c
just do it by simple unitary method
got it?

[@d!_†oX!©]

see, acc. to u
0.7C - 1 mm
so 1C = 1/0.7 mm

so wt i didnt understand is y u did (50*0.7)
cuz 50 is the temp and 0.7 is also the temp at 1mm....so shudn't it be 50*0.7
bt if i do that den the answer is wrong....plsss dude tell me some way to get this thing rite into my head!!!

[cooldude]

see, acc. to u
0.7C - 1 mm
so 1C = 1/0.7 mm

so wt i didnt understand is y u did (50*0.7)
cuz 50 is the temp and 0.7 is also the temp at 1mm....so shudn't it be 50*0.7
bt if i do that den the answer is wrong....plsss dude tell me some way to get this thing rite into my head!!!

dude 0.7 is not the temperature at 1 mm it is the value of the temperature of that changes for each increase in 1mm. theyve just given u 12mm-82mm to confuse u. this is the same as 1mm-70mm

cuz theyve started from 12 u hve to add 12 to (50*0.7), theres no hard nd fast way to answer it, uve gotta understand wat there askin and then answer accordingly

[holychalice]

no it shud be 70
check again

[@d!_†oX!©]

no dude...its 47mm nd 70C

nd cooldude...i'm kinda beginning to understand it now...

[nid404]

okk

I will try my best to explain this
Given
at 0^oC=12mm
& and 100^oC=82mm

difference is 70. So if the reading was.....if for 0 and 70 mm, then length would have been 70/2=35mm for 50 degrees....exactly half
so when the startin point is 12^oC...u will add 12 to the difference/2=47mm. I hope ur able to figure out the logic.

The length for 50 degrees would be right in the middle of 12 and 82

[@d!_†oX!©]

yaa i got that 50 one like dt too...wt about the second part???
i really thing cooldude's explanation is gud...bt i really dont wanna forget it again...so pls guys try nd give me ur working ways to..so dt i have some more ways to do it nd i do not forget...

[Ghost Of Highbury]

assume its from 1mm to 70mm

theyre asking 61mm but thats frm their scale, from our scale it wud be...61-12 = 49

so

70mm - 100

49mm - 70

[cooldude]

nid's method is good for the first part and first part only (it is the simplest way by which u can understand this part of the q), but since u have to do the second part also which does nt hve somehting which is half way or quarter way so u hve to do it by the unitary method. if u do both parts by diff methods then u urself will get confused

[@d!_†oX!©]

yaaa dts rite cooldude...
@aadi dts wat i wanna know dude...how did ya get 70 for 49 mm???

[cooldude]

yaaa dts rite cooldude...
@aadi dts wat i wanna know dude...how did ya get 70 for 49 mm???

dude!!!!!!!!!!! i also explained the second part...look!!!!!!!!!!

ill paste it for u--

1^.c=0.7mm
1mm=1/0.7^.c
therefore the length for which there is a temperature change=>61-12=49mm
therfore the temperature at this=>49*(1/0.7)=70^.c
just do it by simple unitary method

and also since the temperature starts from 0, 70 is ur final ans but cuz the length starts from 12 so u hve to consider 12 in every calculation u make wich evry1 is trying to tell u

[Ghost Of Highbury]

sry sry it shud 0 to 70

ok look..
in the range of 12 to 82

they are asking 61

61 is 49 above from 12

so for our scale which 0 to 70, we have to go 49 above from 0 = 0+49 = 49

got it?

[@d!_†oX!©]

@ cooldude chill man...i've seen urs..nd i got it....i said m just looking for alternate ways...!!!stay calm man...take a deep breath in.........and out......cool??!!

@aadi u till didnt get my point man..i know till here...now how did u get 70 fro 49?? is my question.....

[nid404]

okay for the second part assume the same way

so
assuming
 100^o=70mm(82-12)
then x^o= 61mm-12mm

x= 4900/70=70^o


      

[cooldude]

@ cooldude chill man...i've seen urs..nd i got it....i said m just looking for alternate ways...!!!stay calm man...take a deep breath in.........and out......cool??!!

@aadi u till didnt get my point man..i know till here...now how did u get 70 fro 49?? is my question.....

k dude, By the way just look at my last post ive told u a few things, let other ppl give their views nw