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ALL CIE PHYSICS DOUBTS HERE !!!
astarmathsandphysics:
s08 p2
a) s1 closed so no current or power
b) s1 and s2 closed so voltage acros A is 240 so power is 1.5KW
c)1.5W+1.5KW since voltage across ABC is 240V, 0V and 240V resp
d)voltage across A and B is 120V so using P=V^2/R power in each element is 1/4 of 1.5KW=375 W and total power is 750W
e)voltage across A and B is 120V so using P=V^2/R power in each element is 1/4 of 1.5KW=375 W and total power is 750W +1.5KW in C=2.25KW
Can you upload S09 P21 Q5b cos I don't have it :-[
$!$RatJumper$!$:
--- Quote from: astarmathsandphysics on November 09, 2010, 11:27:35 pm ---s09 p2
a)s1 closed no no current or power
b) s1 and s2 closed so voltage acros A is 240 so power is 1,5KW
c)1.5W+1.5KW since voltage across ABC is 240V, 0V and 240V resp
d)voltage across A and B is 120V so using P=V^2/R power in each element is 1/4 of 1.5KW=375 W and total power is 750W
e)voltage across A and B is 120V so using P=V^2/R power in each element is 1/4 of 1.5KW=375 W and total power is 750W +1.5KW in C=2.25KW
Can you upload S09 P21 Q5b cos I dont have it
--- End quote ---
thankx for that :)
ok iv attached s09 here..
and could you also help me with s10 P22 Q4c
ashish:
NOV 2008 p1 no.11
i have done it but a bit like mechanic question
here it is
8.0a = T
2.0a=20-T-6
after solving it i got 1.4ms-2
there is another method of working it! can anyone please help me with the other method !
$!$RatJumper$!$:
--- Quote from: ashish on November 10, 2010, 04:00:49 am ---NOV 2008 p1 no.11
i have done it but a bit like mechanic question
here it is
8.0a = T
2.0a=20-T-6
after solving it i got 1.4ms-2
there is another method of working it! can anyone please help me with the other method !
--- End quote ---
This is how i would have done it. But i do not get the answer as 1.4ms-2. Can someone tell me what im doing wrong. Thankx
The 2kg mass hanging would be the force that pulls the 8kg mass. Since it is hanging gravity would act on it making it have a force of 2*9.81 = 19.62N
Since frictional forces are 6N, we do, 19.62-6 = 13.62N
Thats the resultant force. Now we use F=ma to get its acceleration.
13.62/8 = 1.7 ms-2
Deadly_king:
--- Quote from: $!$RatJumper$!$ on November 10, 2010, 06:41:53 am ---This is how i would have done it. But i do not get the answer as 1.4ms-2. Can someone tell me what im doing wrong. Thankx
The 2kg mass hanging would be the force that pulls the 8kg mass. Since it is hanging gravity would act on it making it have a force of 2*9.81 = 19.62N
Since frictional forces are 6N, we do, 19.62-6 = 13.62N
Thats the resultant force. Now we use F=ma to get its acceleration.
13.62/8 = 1.7 ms-2
--- End quote ---
You cannot take the acceleration to be 9.81 since that would not be the case due to the tension in the string which is linked to the other mass.
Using Newton's 2nd law of motion for the 2kg mass => W - T = 2a
W : weight of the object.(2 x 9.81)
NOTE : Newton's 2nd law applies only to the resultant force. Here the resultant is W - T.
So you have to do it the way ashish did it. You need to find two equations involving the two variables you're to find; acceleration and tension.
Then you need to solve them simultaneously to get the required solution which is a = 1.4ms-2.
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