Physics: Post your doubts here!

[Mustehssun Iqbal]

q.4 tasty! readings between. 1.98A to 2.02A involves 4 values or 4 readings in total. so the uncertainty for one reading is .01, so total uncertainty will be .04. u will write as 2.00 +- .04.

12) u know that friction always opposes the motion, i.e upwards in this case as the object is travelling downwards. resultant force is zero as all forces are balanced that's why the object is moving with CONSTANT velocity.

33) its a fact. we must see the book for the I/V diagrams for thermistor, lamp, semiconductor and a metal wire. as the temperature increases the resistance increases as well. I = V/R current and voltage are inversely proportional to the resistance.

36) you need to calculate internal resistance first. you are given with the terminal voltage (i assume u know this term) make two equations by keeping in MIND that current is same. I = 1.5 / R1 ( r1 is the internal resistance and 1.5 is the voltage used by the internal resistance as 9-7.5 = 1.5 wohoo !!!!! ) 2nd equation is I = 9 / 15 + R1 , now equate both equations and you will get R1 to be 3 Oooohmzs! I = 9 / 18 = .50 Ampere or you could have simply divided the 7.5 by 15 to find the current in the circuit. as 7.5 is the voltage used by the resistor excluding the resistance used by the battery. but i told you the previous method for similar questions...

nicely done and told! thanks a bunch! : )

 

[rz123]

nicely done and told! thanks a bunch! : )

ur welcome dude. my concepts are not crystal clear so u better check books as well 4 da relevant concepts. nd correct me if u find any answer wrong thankyou.

 

[Mustehssun Iqbal]

ur welcome dude. my concepts are not crystal clear so u better check books as well 4 da relevant concepts. nd correct me if u find any answer wrong thankyou.

ok. keep up the good works! thanks again! : )

 

[rz123]

ok. keep up the good works! thanks again! : )

haha welcome, i like the space in your smilies at the end caz i know the real one here is too wide, seems as someone is begging n making a weird smile. this one ( ).

 

[zain786]

i highly doubt dat, if u somehow find the marking scheme then kindly upload.
for 3: homogeneity test of equations: means the base units on both side of the equations should be same not taking the numerical values on the both side into consideration. i.e v= m/s , now any option after passing this test equal to m/s then that equation is correct. apply to A, underoot ms^-2 into m this will eventually equal to m/s. hence A option is correct.

4) i think its B, as the human reaction error must be about .2 seconds thats why delay on the time axis (not sure)

5) C ? :/ , as V = 3% error multiplied by two , R is 2% error total 8 % error. i dnt remember exactly but there is a way to do this like the power goes down with V we need multiply by 2 the error.....

6) its D, the resultant will originate from the same point as the other 3 forces, now the resultant is springing outwards, we can't show dat on a 2D paper, so it will be D as resultant can't be into the plane or downwards u know..

thnxheaps my bro!!!!!!!!! that helpd alot

 

[rz123]

thnxheaps my bro!!!!!!!!! that helpd alot

No problem!!!!!!!!!!!!!!!!!!!!!!!!!! dat helped me 2!!!!!!!!!!!!!! partyyyyyyyyyyyyyyyyy!

 

[zain786]

No problem!!!!!!!!!!!!!!!!!!!!!!!!!! dat helped me 2!!!!!!!!!!!!!! partyyyyyyyyyyyyyyyyy!

hahahaha great....

 

[yashmehta96]

hey guyz please help me with this question . its about earths magnetic field.
november 2009 paper 4
question 6 C

 

[Sana101]

In oct/nov 2007 question number 3 b) in order to find the gain in p.e why is this step carried out
" (61 – {61 cos18} =) 3.0 cm"
whats the logic behind it?
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w07_qp_2.pdf
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w07_ms_2.pdf

 

[Sana101]

In oct/nov 2009, how do we solve Q4- PART C - part ii)2
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w09_qp_22.pdf

 

[leadingguy]

In oct/nov 2007 question number 3 b) in order to find the gain in p.e why is this step carried out
" (61 – {61 cos18} =) 3.0 cm"
whats the logic behind it?
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w07_qp_2.pdf
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w07_ms_2.pdf

AOA
gain in g.p.e depends up on the height to which the object raised.

so for calculating the increase in height from the initial position we have to use the formula 61.cos(18

by this we will get the distance covered by the string which is 58cm
now how much is the string raised initially?? subract 61 - 58 U will get 3cm.

this 3cm is the increase in height from ground.

NOW calculate g.p.e = mgh (51/1000)(9.81)(3/100) = 1.5*10^-2Ans

 

[rz123]

In oct/nov 2009, how do we solve Q4- PART C - part ii)2
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w09_qp_22.pdf

hi, c ii) 1 part) we know the spring constant dat is 181 N/m.
3.8 N + F = 181 into 1.5/ 100 , the extra force will be 1 N applied in the 3rd diagram. use this to find the mass. W=mg , total force is now 4.8N , 4.8= m into 9.8 , mass is 0.4kg , calculate the change in g.p now, 0.4 into 9.8 into change in legth which is 0.015m. this will come 0.05 Joules.

2) elastic potential energy formula = 1/2 k x^2 , k we know already, to find the extension u need to minus the extension of the 3rd spring compared with the unextended length in the spring this will be 0.036 , minus this extension with the previous spring extension dat too will be compared with the unextended length. i.e 16.3cm-14.2cm = 0.021 meters. we have all the values to calculate the change in elastic potential energy. 1/2 into 181 into (0.036 squared - 0.021 squared) this will give u 0.077 joules.

3) workdone is the energy consumed after we subtract the elastic potential energy in the spring with the change in gravitional potential energy in the process.. 0.077-0.05 = 0.020Joules Yuppie!

 

[Mustehssun Iqbal]

Assalamu alaikum,
Q) In the circuit shown in Figure 10.35, what is the effective resistance between the points A and B??

 

[rz123]

Assalamu alaikum,
Q) In the circuit shown in Figure 10.35, what is the effective resistance between the points A and B??

1st of all lol at your drawing skills

is it 40 ooohms?
the ones in parallel might be calculated like this. 1/10 + 1/10= 1/R , and then 30 ohms in series i.e along the line from A to B point will be added. total 40. not sure.

 

[Mustehssun Iqbal]

1st of all lol at your drawing skills

is it 40 ooohms?
the ones in parallel might be calculated like this. 1/10 + 1/10= 1/R , and then 30 ohms in series i.e along the line from A to B point will be added. total 40. not sure.

hahaha at your comment on my drawing.
the book says it's 10 ohms.
It's from Pacific vol. 2, exercise 10.3, Q.8.
You couldn't do it. That means it's a challenging question. q:
thanks for trying though. : )

 

[rz123]

hahaha at your comment on my drawing.
the book says it's 10 ohms.
It's from Pacific vol. 2, exercise 10.3, Q.8.
You couldn't do it. That means it's a challenging question. q:
thanks for trying though. : )

maybe its like this. the current BYPASSES at the beginning travel upwards where a 10 ohm resistor is present. the resistor above is parallel with the resistor at the end of the line Ab. now the 10 ohm resistor at the end is also parallel to the 10 ohm resistor below as well. the lower loop i mean. so altogether it will be like 1/10+ 1/10 = 1/R and then again 1/10+1/10 =1/R. it will be 10 ohms. still not sure and confused about this one. need to go back towards book for the concept. ur welcome.

 

[Mustehssun Iqbal]

yeah that makes sense. Thanks!

 

[Mustehssun Iqbal]

Here's another question regarding DC circuits:
Calculate the resistance of the network shown below:
(a) between A and B;
(b) between A and C.
Editted:
Answers are 3 ohms and 4 ohms of a and b respectively.

 

[unique840]

Here's another question regarding DC circuits:
Calculate the resistance of the network shown below:
(a) between A and B;
(b) between A and C.
Editted:
Answers are 3 ohms and 4 ohms of a and b respectively.

A) between A and B: means current is entering at A and leaving at B. when this happens, the circuit is as shown. means the passage of current is either directly from A to B or from A-D-C-B. we will take both the passages in parallel. so the calculation for parallel resistance would be:
1/R = 1/12 + 1/4
R= 3 ohms

 

[unique840]

Here's another question regarding DC circuits:
Calculate the resistance of the network shown below:
(a) between A and B;
(b) between A and C.
Editted:
Answers are 3 ohms and 4 ohms of a and b respectively.

b) the current will enter at A and leave at C. it will either follow A-B-C or A-D-C. take both passages in parallel. it will be:
1/R = 1/8 + 1/8
R = 4 ohms