Physics: Post your doubts here!

[DragonCub]

CAN ANYONE SOLVE THIS ONE..

M/J 2006 (Paper 4)

Question (1)
b(i) Show that, for the rocket to travel from a height R to a height 2R above the planet’s
surface, the change ΔE(p.e) in the magnitude of the gravitational potential energy of
the rocket is given by the expression

ΔE(p.e) = GMm/6R

Use change in gravitational potential times mass.
At height R, distance to Earth's centre is 2R. phi = -GM/2R
At height 2R, distance is 3R. phi = -GM/3R
Change in phi = -GM/3R - (-GM/2R) = GM/6R
ΔE(p.e) = Δphi × mass = GMm/6R

 

[namename]

I'm pretty sure that there is an error in the mark scheme . in question 2 b iii)
Do you guys agree?

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w10_qp_42.pdf

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w10_ms_42.pdf

Heating supplied suddenly became 0. WHY?

 

[Wanzi21]

http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s06_qp_2.pdf

Assalamualaikum
I need your help for question 3 on all parts
your help will be fully appreciated ^^

 

[Aahliya]

Use change in gravitational potential times mass.
At height R, distance to Earth's centre is 2R. phi = -GM/2R
At height 2R, distance is 3R. phi = -GM/3R
Change in phi = -GM/3R - (-GM/2R) = GM/6R
ΔE(p.e) = Δphi × mass = GMm/6R

Thanks Dragon..

 

[Aahliya]

Anyone who can solve this :
M/J 2007
Question 3(b) The area below the line of the graph of Fig. 3.2 represents the potential difference
between A and B.
Use Fig. 3.2 to determine the potential difference between A and B.
potential difference = …………………………. V

 

[elbeyon]

voltmeter and resistor is in parallel so resistance would be 1/R= 1/200 + 1/200=1/100 so R= 100 kilo ohm and i just simply used the formula V=IR

Ok I'm clear now. Thanks a lot.

 

[Scafalon40]

http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s09_qp_2.pdf
Q 5 please

 

[confused123]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s09_qp_2.pdf
Q 5 please

first variant or second variant dude? or p22 or p21?

 

[namename]

Sumone try to solve this?
isn't mean power=0.5 (Vmax^2/R) ??

why does the mark scheme just takes power=Vmax^2/R ??

btw this is A.C 9.9sin(220t)

from s11 q43 6 b)

 

[USMAN Sheikh]

HElp needed for aslevel practicals !!! how to do the part that has describes a relation means h is directly proportional to x^2 ?
1st exp result H= 7.5 cm x=4.0
2nd exp result H=31.2 x=8.50

 

[USMAN Sheikh]

PLS reply asa[p ?????

 

[hmlahori]

Can anyone please explain this question from paper 2?

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s11_qp_21.pdf
Q number 5 part B

 

[USMAN Sheikh]

Hm lahori can u help me pls

 

[hmlahori]

PLS reply asa[p ?????

HElp needed for aslevel practicals !!! how to do the part that has describes a relation means h is directly proportional to x^2 ?
1st exp result H= 7.5 cm x=4.0
2nd exp result H=31.2 x=8.50

This is quite easy. Its just about proportionality.
You are usually asked to find the constant (k) and compare the values to see if the relation is correct.
If from the two sets of values that are given the values of k found are equal or very close to each other the relation is correct if not then the relation is wrong.

If 'h is directly proportional to x^2' that means H=kx^2 that also means (by making 'k' the subject of the formula) k= H/x^2
now two sets of values for H and X are given. From both we will calculate a value of k

1st exp result H=7.5 cm and x=4.0
K= H/x^2
= 7.5/4^2
=0.47

2nd exp result H=31.2 and x=8.50
K= H/x^2
= 31.2/8.50^2
= 0.432

These two calculated values of K are very close to each other concluding that the relation 'H is directly proportional to x^2' is correct.

Hope this helps!

 

[Scafalon40]

first variant or second variant dude? or p22 or p21?

21

 

[Aahliya]

Anyone who can solve this :
M/J 2007
Question 3(b) The area below the line of the graph of Fig. 3.2 represents the potential difference
between A and B.
Use Fig. 3.2 to determine the potential difference between A and B.
potential difference = …………………………. V​

 

[USMAN Sheikh]

IN paper three that is practiacl there is a common ques " JUSTIFY THE NUMBER OF SIGNIFICANT FIGURES ? " how to solve that ?

 

[USMAN Sheikh]

????? w8ing

 

[hmlahori]

IN paper three that is practiacl there is a common ques " JUSTIFY THE NUMBER OF SIGNIFICANT FIGURES ? " how to solve that ?

This question basically means to what significant figures u have given your answer to and why.
You should mention the number of significant figures you have given in your answer to and say that it depends on the significant figures of the values that were used to calculate that answer.
For example a question says: Find the distance a car covered in 23.6 seconds travelling at a speed of 3.84m/s.
the answer would be given to 3 significant figures as both the values are given to three significant figures.

 

[confused123]

IN paper three that is practiacl there is a common ques " JUSTIFY THE NUMBER OF SIGNIFICANT FIGURES ? " how to solve that ?

i think you have to give a reason like this that you have been giving your answers in the previous measured quantities in 3 s.f so that's why using the same number of s.f throughout.