Physics: Post your doubts here!

[A.ELWY 7]

help pls im stuck in this......T1 sin(50) + T2sin(40)=7.5... how to continue the equation to get T1 nd T2, pls i need a quick reply with details..thanx very much

 

[confused123]

acceleration should be constant...

and the 2nd?

 

[anonymous123]

one individual spring will have an extension of x... when connected in parallel they will have an extension of .5x.... extension will be divided equally between the 2 springs... when another spring will be connected in series to them, the extension will again be added up... .5x+x giving 1.5x...

i got it logically but i cant do the working..plz help me

 

[confused123]

yes plz explain..

see in parallel springs we calcualte spring constant by applying this formula: k + k ...

and springs in series the spring constant is calculate by 1/k + 1/k....

so there are two springs in paralel F= kx , spring constant for these two springs is k + k = 2k
extension for these two springs is 2x
for the spring in series with these two springs the constant k is 1/k
extension for this spring is 1/2x
total extension:-
1/2x + 2x = 3x/2

 

[anonymous123]

see in parallel springs we calcualte spring constant by applying this formula: k + k ...

and springs in series the spring constant is calculate by 1/k + 1/k....

so there are two springs in paralel F= kx , spring constant for these two springs is k + k = 2k
extension for these two springs is 2x
for the spring in series with these two springs the constant k is 1/k
extension for this spring is 1/2x
total extension:-
1/2x + 2x = 3x/2

Jazakallah i get it now

 

[confused123]

Jazakallah i get it now

Subhanallah i am not sure how did i calculated this answer. caz F = kx , i just added up kx from both springs...

 

[anonymous123]

9702 s06 qp 2
Q1 c part ii

in the ms 2 justifications are provided...can sm1 elaborate dem plz

 

[Most_UniQue]

How was physics p33? Mine went great although the experiment a bit hard to set up ...

 

[Sanis]

guyz can u tell me 3 ways of reducing random errors other than "repeating the experiment"

 

[confused123]

guyz can u tell me 3 ways of reducing random errors other than "repeating the experiment"

yeah take several readings and then take the average, avoid carelessness while taking readings, reducing human error

 

[confused123]

9702 s06 qp 2
Q1 c part ii

in the ms 2 justifications are provided...can sm1 elaborate dem plz

what i got is that in order to have negligible resistance the weight should be more then the upward force, and it is after calculation. if drag forces were present then the forces would be closer or equal. not the case here.

 

[Jaf]

What is the direction of force on the charges in this question and why? (6b) :
http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s05_qp_2.pdf

The mark scheme doesn't mention anything. The examiner report is unhelpful too. :|
Also, this is a question that has been repeated in a recent paper.

Thanks!

 

[Oliveme]

Please help me with this question In physics paper 23, question 2 part (c). I have no idea about vector triangles. http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_23.pdf

Thank you very much.

Please answer the question above!
http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s10_qp_23.pdf

 

[anonymous123]

what i got is that in order to have negligible resistance the weight should be more then the upward force, and it is after calculation. if drag forces were present then the forces would be closer or equal. not the case here.

i didnt get the first statement...in almost every case the weight of a body is greater thn resistance for some tym b4 it reaches its terminal velocity. i do get that the resistance is very small compared to the weight in dis case but wht if the resistance was 0.01N cud it still be neglected? dat is smaller thn the weight so can we ignore it as the ms seems to imply? i dnt think so..plz explain further

 

[confused123]

i didnt get the first statement...in almost every case the weight of a body is greater thn resistance for some tym b4 it reaches its terminal velocity. i do get that the resistance is very small compared to the weight in dis case but wht if the resistance was 0.01N cud it still be neglected? dat is smaller thn the weight so can we ignore it as the ms seems to imply? i dnt think so..plz explain further

i can't. you need to discuss with some teacher.

 

[confused123]

What is the direction of force on the charges in this question and why? (6b) :
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s05_qp_2.pdf

The mark scheme doesn't mention anything. The examiner report is unhelpful too. :|
Also, this is a question that has been repeated in a recent paper.

Thanks!

6.i)draw arrows in the direction of the field. i.e downwards for the positive charge and upwards for the negative one.

ii)we are given with the electric field strength in the a part which is : 2 into 10^3 V/m

Electric field strength = Force / Q

2 into 10^3 into 1.2 into 10^-15 = Force , force is 2.4 into 10^-12 N

iii) Torque of a couple = Force into perpendicular distance between two forces

2.4 into 10^12 into 0.0025 sin 35 ---> torque is 3.44 into 10^15 Nm

iv) the subsequent motion is to rotate in order to align with the field.

P.S these are basic concepts and formulas maybe that's why marking scheme and examiner reports didn't go into details.

 

[Jaf]

6.i)draw arrows in the direction of the field. i.e downwards for the positive charge and upwards for the negative one.

Why is the direction the way it is? I don't get it.

 

[confused123]

Why is the direction the way it is? I don't get it.

i was expecting a thanks for the other answers but anyway..

i guess the arrow with the positive charge will be towards right and down and the arrow with the negative charge will be towards left and up together trying to rotate the object

 

[Jaf]

i was expecting a thanks for the other answers but anyway..

i guess the arrow with the positive charge will be towards right and down and the arrow with the negative charge will be towards left and up together trying to rotate the object

I - uh - didn't ask for the other answers.

And are you sure you meant to say right AND down, and left AND up instead of right and left OR down and up? Because the former wouldn't make sense. You'd have directions pointing in both, the clockwise and anticlockwise directions. :/

Part of my original question remains unanswered. Why would they behave in a such a way? Are charges supposed to line up parallel to the direction of the field?

 

[Brains]

What is the effect of springs in series and parallel on extension and spring constant? can somebody plz help me with this...

+

does anybody know which derivations are in our course?