Physics: Post your doubts here!

[Suchal Riaz]

Progressive wave equations are not mentioned in syllabus but are given in Pacific Physics Volume 2. Should i do it?

 

[jhon134]

please help me with these questions also

 

[selena]

How much percentage does each paper hold(p1,P2,p3)??

 

[selena]

I have two physics As practical questions
1-:how do you solve the part after the graph part of the paper where an equation is given and you have to find one of the values in the equation
2:-do you get marks for showing average readings in the table for example one column for "t1" and another for "t2" and a third one for "t" which is the average

 

[daredevil]

I have two physics As practical questions
1-:how do you solve the part after the graph part of the paper where an equation is given and you have to find one of the values in the equation
2:-do you get marks for showing average readings in the table for example one column for "t1" and another for "t2" and a third one for "t" which is the average

1) make an equation of y=mx + c according to what you took on the x-axis and the y-axis and then compare the equation. if u have a problem still then tell me or give me an example or something.

2) yes you do get marks. it counts as an accuracy level and in some marking schemes they even REQUIRE the average (mean). u never know wen they will say that they definitely need it. erring on the safe side is better so u should take averages wherever possible like in the case of time, like u said, you can take 't1' , 't2' and then <t> which is the mean. always write mean time life this in the heading yourheading should be
(t1+t2)/2 = <t>
however in certain cases like taking voltage from a voltmeter, you get one digital value so there you need to judge if you can take the mean there or if there is no chance of the value varying and stuff. let the scientist in you speak up for that =)

 

[SilverCrest]

Why is the ans D and not B?

In the above question how do we know if the answer is A or C?the correct ans is A btw

 

[daredevil]

View attachment 33604


Why is the ans D and not B?
View attachment 33606
In the above question how do we know if the answer is A or C?the correct ans is A btw

it is a parabolic path. consult your graphs for parabolic motion. there is not a uniform increase of energy. The curved path shows a non-uniform increase of height which means a non-uniform decrease of velocity thus the answer is D.


In the next questions, you can see that Q is pointing downwards. C is pointing upwards and A is pointing downwards. If you will add P and Q the arrow should be pointing downright. That is why the answre is A and not C!

 

[shazmina]

Assalamu Alaikum Can some one please help me with question no 18,19,32 & 36 of this paper.....
http://www.freeexampapers.com/index.php/directory/download?location=A Level/Physics/CIE/2002 Nov/9702_w02_qp_1.pdf
Thanks in Advance

 

[Mubbasher Iqbal]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_13.pdf

Q10...can someone solve this asap?

 

[IGCSE O/L student]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_13.pdf

Q10...can someone solve this asap?

we'll take this problem in terms of the forces acting on the barrel and the man
for the barrel: the force due to the barrel - the tension in the rope(T) = ma (because the barrel move's down, the force due to the barrel is greater than the tension)
(120*10) - T = 120a (we dont know the acceleration of the man and the barrel)
for the man: the tension (T) - the force due to the man = ma
T - (80*a) = 80a
find the value of a using simultaneous equations, which is 2 ms^-2
using v^2=u^2 + 2as
find the final velocity of the man at 9 m, taking u as 0 ms^-1

 

[shazmina]

SOMEBODYYY PLEASEEEEEEEEEE HELP!!!!
A filament lamp and 220 ohm resistor are connected in series to a battery of e.m.f. 6.0 V . The battery has negligible internal resistance. A high-resistance voltmeter placed across the resistor reads 1.8 V.
Calculate :
a) the current drawn from the battery
b)the p.d across the lamp
c) the total resistance of the circuit
d) the number of electrons passing through the battery in a time of 1.0 minute.
(the elementary charge is 1.6x10^-19 C.)

For part A .. the pd across the resistor and the resistance is already given ..and so you can easily find out the current passing through it by using the formula I=V/R
so its going to be 1.8/220 which gives 8.2*10^-3A
As they have said negligible internal resistance u dont have to consider the resistance of the cell or the wires...

For part B...as they are in series connection the sum of the potential drops around the loop is equal to the emf of the cell ..so u have the pd of the resitor and the emf and so u can minus them to get the pd of the lamp..
which is 6-1.8=4.2V

For part C... in order to find the total resistance first find the resistance of the lamp which is 4.2/8.2*10^-2 ( same current value as they r in serise ) =513ohms
then find the total resitance by adding both the resistance of the resistor as well as the lamp whihc is 513+220733ohms

For part D...For this u need to know the charge ...therefore Q=It... (8.2*10^-2) *(1*60)secs =0.49C
then use the formula Q=ne and substitute in the equation
n=Q/e
...
0.49/1.6*10^-19 = 3.06*10^18 ( 3.1*10^18)

 

[SilverCrest]

@shazmina
Q18
workdone =mgh
=2.0*10*1.3*10^9
=2.6*10^10
Power =workdone/time
totaltime in one day=60*60*24
power=2.6*10^10/86400
=300kW
ans= D
Q19
assume mass of the twig is 1kg
sixty percent of potential energy is converted to kinetic energy
60% of mgh =(10)(1)(200)(.6)
=1200
1200=K.E
1200=(.5)mv^2
v=48.9
~49

 

[SilverCrest]

it is a parabolic path. consult your graphs for parabolic motion. there is not a uniform increase of energy. The curved path shows a non-uniform increase of height which means a non-uniform decrease of velocity thus the answer is D.


In the next questions, you can see that Q is pointing downwards. C is pointing upwards and A is pointing downwards. If you will add P and Q the arrow should be pointing downright. That is why the answre is A and not C!

for the first question there is a uniform decrease in velocity(rate of change of height) because the acceleration is constant,no?

 

[shazmina]

@shazmina
Q18
workdone =mgh
=2.0*10*1.3*10^9
=2.6*10^10
Power =workdone/time
totaltime in one day=60*60*24
power=2.6*10^10/86400
=300kW
ans= D
Q19
assume mass of the twig is 1kg
sixty percent of potential energy is converted to kinetic energy
60% of mgh =(10)(1)(200)(.6)
=1200
1200=K.E
1200=(.5)mv^2
v=48.9
~49

Thank you soooooooooooo much

 

[daredevil]

for the first question there is a uniform decrease in velocity(rate of change of height) because the acceleration is constant,no?

no i don't think so. it's parablic motion. have you done parabolic yet? i don't know maybe i'm wrong but that's what i think is right. maybe someone else canhelp. @A star @syed1995 anyone?

 

[Mubbasher Iqbal]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w11_qp_12.pdf
q16

 

[syed1995]

no i don't think so. it's parablic motion. have you done parabolic yet? i don't know maybe i'm wrong but that's what i think is right. maybe someone else canhelp. @A star @syed1995 anyone?

highlighting me for an AS question.? Good Call!

Well first of all.. there will always be horizontal component of velocity so that's that which will be uniform since Gravitational Acceleration has no effect on it. Now in the vertical component of Velocity Gravitational Acceleration will affect it.. as it goes up the acceleration will be -ve and there will be a decrease in speed and when it goes down acceleration will be positive and there will be an increase in the velocity... it won't be uniform because V^2 = (Vhor^2 + Vver^2) (Simple Pythagoras Theorem).. a square root will never give you a straight line remember that so answer is D.

 

[Snowysangel]

Could sb please tell me why, when generating electrical power, the electrical power output would be less than the power available from a source such as the wind or the sun. How would power be lost

 

[daredevil]

highlighting me for an AS question.? Good Call!

Well first of all.. there will always be horizontal component of velocity so that's that which will be uniform since Gravitational Acceleration has no effect on it. Now in the vertical component of Velocity Gravitational Acceleration will affect it.. as it goes up the acceleration will be -ve and there will be a decrease in speed and when it goes down acceleration will be positive and there will be an increase in the velocity... it won't be uniform because V^2 = (Vhor^2 + Vver^2) (Simple Pythagoras Theorem).. a square root will never give you a straight line remember that so answer is D.

hahha making good calls *like a boss*

@SilverCrest here you go

 

[hamzashariq]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w08_qp_1.pdf
Q.10
the answer is D. but why?? shouldn't it be u1-u2 since they are in opposite direction??