PHYSICS AS HELP

[Hateexams93]

http://www.xtremepapers.me/CIE/Internat ... 7_qp_2.pdf Question 6 , b second part , why do we have to multiply by 2 , i thought i need to divide it by 2 can't get the reason

 

[Hateexams93]

peopleeeeeeeeeeeee..can some1 plz anwer to my question

 

[yubakkk]

ya then the reasult will same

 

[libra94]

Resistance = (resistivity )* (length)/ area
there are 2 wires, so the length will be 2l , so u multiply the length (16m) by 2 !!

 

[thunderingthunder]

Resistance = (resistivity )* (length)/ area
there are 2 wires, so the length will be 2l , so u multiply the length (16m) by 2 !!

Dont we have to calculate the cross sectional area of each wire??so y will v multiply it wid 2??? :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock: :shock:

 

[libra94]

oh righttt, its 6b(ii)
hmmm yeah it must be divided by two!!
well maybe the marksheme is wrong, cuz its sometimes wrong too!!

 

[Hateexams93]

are u sure ?

 

[libra94]

NO NOO..THE ANSWER IN THE MARKING SCHEME IS CORRECT:
R = ρL / A
0.11 = (1.8 × 10–8 × 16 × 2) / A
A = 5.3 × 10–6 m
they multiplied the length by 2!!
then they substituted to get A in the equation!!!!

 

[Hateexams93]

hhhhhh...its soo confusing ..why can't we find the area first , and then divide by two ?

 

[libra94]

whats so confusing?? tell me i'll try to help u
why would u divide it by two??

 

[Hateexams93]

http://www.xtremepapers.me/CIE/Internat ... 5_qp_2.pdf AND ONE MORE QUESTION number 4 , a (ii) how can e find the area of the loop ?? i mean the distance

 

[libra94]

u use the equation s=ut+1/2 at^2
u is 0, so the equation will be s=1/2 at^2

 

[Hateexams93]

use of area of loop B1
distance = 0.031 ± 0.001 m B2 [3]
allow 1 mark if 0.031 ± 0.002 m)
thats the answer from the ms ,

 

[libra94]

but why cant we use the equation??

 

[libra94]

are we getting the same answer using the equation or not?

 

[Hateexams93]

i have no idea , probably because its acceleration keeps changing , so how to find the distance ?

 

[Hateexams93]

no the answer is different

 

[Hateexams93]

so what is the answer ???????? how do we use the graph ?

 

[libra94]

im getting 0.027!!
i make 2 straight lines, starting frm 0 till 0.3 on the middle top
then i found the area under 2 triangles.. i gt 0.024 m
then i count the number of boxes in the area that was not part of the triangle...and then i cross multiplied
i got 0.027!!!

 

[Hateexams93]

lol can we use integration formula ?