Physics: Post your doubts here!

[Muhammad Talha]

http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9702%20-%20Physics/9702_s09_qp_1.pdf
Plz solve these ques:
2,13,14,15,18,20,21,25,33....
Plz reply asap.....

 

[rz123]

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s09_qp_1.pdf
Plz solve these ques:
2,13,14,15,18,20,21,25,33....
Plz reply asap.....

hi, this is my try:-

2) in this mcq you are given with the angle and horizontal component.use it to find the vertical comp.
Tan30 = Perpendicular / 20 , it comes 11.5N i.e C.

13) no convincing ans but the weight is making a torque of 180 Nm, how? 900 N into .20m (.20 is the perpendicular distance or the radius of the disc)
same torque will be shifted upwards in order to lift this weight i.e 180 = F into 1.20 m it comes 150 N hence B. ( i dnt knw why i took .20 as the perp distance to find the torque created by weight)

14) Power = F v , so k = P over v^3 because you need to add another v in the denominator as F = Power over velocity.

15) what i get is dat if u c in both vessels the height will decrease by half from the original height in the vessel X, means h will bcm h/4 altogether, so the answer will be B mgh/4.

18) pressure = pgh , p ang remain constant. u know that h has increased in the right side of manometer. i.e pressure has increased. there is only option D 2pgh which supports this idea. other three options shows decrease or no change in the pressure.

20) extension directly proportional to length and inversely proportional to area. length is twice so this increase the extension by 2, area has decreased as well by half so this also doubles the extension, total extension raised by 4 times. the ratio of the tension will be 4 /1. (not so clear i know)

21) strain energy = 1/2 F into x so 1/2 into 17 into 30 /100 it comes around 2.5 J but the best estimate would be less then that i.e 2 Joules which is nearest to the whole number. 3J would be very higher i.e A option

25)i dnt understand , it shud be C but its A, d sin Q = n lambda , this s what comes after moving here nd dre things
n/N = sin Q / Lambda

33) U must see that the two cells are not in one direction, cancelling each others voltage. i.e subtract these two 3V- 1.2 V = 1.8 Volt , now use this to find the current in loop 1 which has 9 ohm resistor. I = 1.8 / 9 = .20 Ampere i.e B.

 

[zain786]

can anyone plz upload the answers to these....thnx

 

[Mustehssun Iqbal]

Assalamu alaikum,
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w08_qp_1.pdf
Q.4,12, 33 and 36. Thanks in advance!

 

[rz123]

can anyone plz upload the answers to these....thnx

answers to the all questions? i don't think that will be feasible. if any specific question then tell me.

 

[zain786]

answers to the all questions? i don't think that will be feasible. if any specific question then tell me.

bro ther must be some1 whose done em all....anywayz thnx for lookng...the qs i need help in...are:
3, 4, 5, 6

 

[rz123]

Assalamu alaikum,
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w08_qp_1.pdf
Q.4,12, 33 and 36. Thanks in advance!

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...

 

[rz123]

bro ther must be some1 whose done em all....anywayz thnx for lookng...the qs i need help in...are:
3, 4, 5, 6

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..

 

[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!