Physics: Post your doubts here!

[Ahmad Zaeem]

snowbrood
the distance of block from the level of head of the man is 18m and when to level the head with the block man travels 9m upwards and block 9m downwards.
tension acts towards the pulley and the weight acts opposite to tension i.e downwards.
force acting in the direction of acceleration is considered more in magnitude than the force in opposite direction

for the man
T-80g=80a equation 1
120g-T=120a equation2
adding both equations we get
40g=200a
a=0.2g (given g as 10ms^-2)
a=2ms^-2
v^2=2as (as initial velocity of both the objects is zero )
v^2=2*2*9
v^2=36
v=6ms^-1

i understood qs 24 very well ....but still haven't got an idea about this qs 12...plsss...label the words "a"...etc...and write eqs first ....like mg=ma ...what ever is the equation.... i am sorry for the inconvinience but i am a medical student ....and mathematics has always been my enemy .... ...lol

 

[Ahmad Zaeem]

May june 2012.. Paper 11 Q34 ....i really don't have the ideo hoe to solve these kind ov qs!!!....need help with a concept pls. (-_*)

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_11.pdf

 

[littlecloud11]

May june 2012.. Paper 11 Q34 ....i really don't have the ideo hoe to solve these kind ov qs!!!....need help with a concept pls. (-_*)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_11.pdf

For these questions it's easier if you compare ratio of the two resistance. The resistance of the first wire is R, let the resistance of the second be R2.
Now, you know that resistance = (resistivity* length)/ cross-sectional area.
So, R/ R2 = [(Resistivity* L1)/ A1]/[(Resistivity* L2)/A2]
for the same material the resistivity is the constant. So, cancel resistivity and cross-multiple and you get R/ R2= L1*A2/ L2*A1
once you understand this ratio you can start from here for all such question in future. Just put the values in now and remember to convert all the units for radius to meter. Area of cross-section Pi r^2 but again, you can cancel out pi for both. So it's just length*radius^2
you get, R/R2 = 8* (5*10^-4)^2/ 2* (2.5*10^-4)^2
that is, R/R2 = 16
so R2 = R/16

It might seem a little confusing but just write it out as you go and it gets simpler. Hope this helps!

 

[mizmoody]

here u go

Thanks

 

[Ahmedraza73]

Can anyone Post AS level Physics Waves Past Papers Unsolved?

 

[Dug]

Can anyone Post AS level Physics Waves Past Papers Unsolved?

Here

 

[Abu mota]

plz help me and ty

 

[Ahmad Zaeem]

For these questions it's easier if you compare ratio of the two resistance. The resistance of the first wire is R, let the resistance of the second be R2.
Now, you know that resistance = (resistivity* length)/ cross-sectional area.
So, R/ R2 = [(Resistivity* L1)/ A1]/[(Resistivity* L2)/A2]
for the same material the resistivity is the constant. So, cancel resistivity and cross-multiple and you get R/ R2= L1*A2/ L2*A1
once you understand this ratio you can start from here for all such question in future. Just put the values in now and remember to convert all the units for radius to meter. Area of cross-section Pi r^2 but again, you can cancel out pi for both. So it's just length*radius^2
you get, R/R2 = 8* (5*10^-4)^2/ 2* (2.5*10^-4)^2
that is, R/R2 = 16
so R2 = R/16

It might seem a little confusing but just write it out as you go and it gets simpler. Hope this helps!

Got it very well!!!!....thanks alot!!!!!!......wasn't confusing even a bit ....!!!

 

[littlecloud11]

Got it very well!!!!....thanks alot!!!!!!......wasn't confusing even a bit ....!!!

Glad you did.

 

[Norton]

9702/12_2011 Oct\Nov paper 12
Can Somebody PLEASE Give Reasons and concepts to the answers....................pls..pls..pls...
I'm in a hurry...............Thanks

 

[Tkp]

the distance of block from the level of head of the man is 18m and when to level the head with the block man travels 9m upwards and block 9m downwards.
tension acts towards the pulley and the weight acts opposite to tension i.e downwards.
force acting in the direction of acceleration is considered more in magnitude than the force in opposite direction

for the man
T-80g=80a equation 1
120g-T=120a equation2
adding both equations we get
40g=200a
a=0.2g (given g as 10ms^-2)
a=2ms^-2
v^2=2as (as initial velocity of both the objects is zero )
v^2=2*2*9
v^2=36
v=6ms^-1

for question 24
stress=F/A
F=stress*A
F=(stress/4)*4A (area would be 4A as (2D)^2 is four times greater than (d)^2 for e.g (2*2)^2=16 x(2)^2=4 see
stress should be divided by 4 as the examiner states that load is the same which means the force applied is the same
so to get F 4 must be divided by 4 to get 1 ok!!

stress is directly proportional to strain
so if stress is stress/4 .strain would also be strain/4
stress/4=x/3l.
stress=x/l main formula
coefficient of x would be such that it equals 3/4 because only then we would get our formula u see coefficients will change but the formula wont ok

dnt we need to find the radius here?

 

[snowbrood]

dnt we need to find the radius here?

no why complicate things when u can solve them by a simpler version

 

[snowbrood]

9702/12_2011 Oct\Nov paper 12
Can Somebody PLEASE Give Reasons and concepts to the answers....................pls..pls..pls...
I'm in a hurry...............Thanks

U THINK IF SOMEONE WOULD SOLVE ALL 40QUESTIONS FOR U THEN STOP DREAMING JUST POST THE QUESTIONS THAT U THINK U CANT SOLVE

 

[Tkp]

guys please help me to solve this questions 10,19,21,23,26,28,29,31,34,36,37,38

 

[confused_soul]

Hiii can some body please help me
In paper 5 phy ! For drawing graph in question it is said to include error bars what does that mean???
We calculate the uncertanties in part 1 !!
What to do for value we plot in the graph?

 

[Tkp]

no why complicate things when u can solve them by a simpler version

help me in oct nov 12

 

[Norton]

Can someone help me to "Design an experiment to show interference of light waves using a laser beam"
for AS level PLZZZZZZZZZZZZZZZZZZZ!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Kumkum]

can someone pls help me with this
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w06_qp_1.pdf
question 4 and 12

 

[Dug]

can someone pls help me with this
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w06_qp_1.pdf
question 4 and 12

4)
T = 1/50 = 0.02s = 20ms
Time-base = 10ms
Therefore, 1 complete wave takes 2 divisions horizontally.

Y-gain = 5V
Amplitude = 5

D is the answer.

12)
Initial Momentum = Final Momentum
1000 x 5 = 10x
x = 500m/s

 

[Kumkum]

4)
T = 1/50 = 0.02s = 20ms
Time-base = 10ms
Therefore, 1 complete wave takes 2 divisions horizontally.

Y-gain = 5V
Amplitude = 5

D is the answer.

12)
Initial Momentum = Final Momentum
1000 x 5 = 10x
x = 500m/s

Jazakallah