Physics: Post your doubts here!

[histephenson007]

How do you effectively find the area under the curves? I knw counting full squares and half-squres... but I always don't get the answer within the range (not problem of reading axis, units)View attachment 7123

I guess counting squares is the best option available. If not that, you may try using Calculus, but you will need the f(x) of the curve to do that. I kinda suck at counting squares too - -

 

[elbeyon]

combined resistance of voltmeter + 200kilo ohm resistor =100 kilo ohm total resistance = 400+100=500 kilo ohm total current across the whole circuit =60/500000=1.2 multiply by 10^-4 so now reading across the voltmeter = 1.2 into 10^-4 multiply by 100000=12V so the answer is A

Thank you for solving but I din't get it properly. Aren't we supposed to use the equation:
Vout=(R2/R1+R2)*Vin

Can you please clearly mention the formula that you used and moreover where did that 100 kilo ohm came from ?

 

[elbeyon]

Q. Describe an experiment to determine the acceleration of free fall using a falling body.

Check this out:
http://mypages.iit.edu/~smart/martcar/lesson2/free-fall-experiment.html

It might seem quite boring but this really helps.

 

[Aahliya]

N=N knot e ^-lemda t
where Nknot = original number of undecayed nuclides at time t=0 so here N knot= 10 because original number was 10 out of which 9 decayed into iron and one was left
N=number of undecayed nuclides after time t so here N=1 as one manganese was left out of the 10 so 1=10e^-lemda t
lemda=0.693/2.6=0.2665 so overall t=ln10/0.2665=0.864hours

Thanks for replying.. but can u plss tell me how did u find the original no. of undecayed nulei and how can u say 9 decayedinto Iron and 1 was left as manganese ?? if u dun mind then can u plss explain me in detail..

 

[namename]

emf is the negative gradient of the given graph

thank you! so negative gradient of B graph is induced E (similar to electric field strength being negative potential gradient huh?) how about the one i posted earlier than that?? (in the same page (75th)

 

[hm12]

So u just put the angle in that equation.. Can u explain the logic behind this.. Moreover, the second question says the phase difference is 240 degrees..
but d= -4cos240 = +2 which means this should also be in the +ve dir, whereas it is negative..

the equation is d=-4cos220t where 220t is equal to omega multiply by t and u know teeta is equal to omega multiply by t so here theeta value is 120 so u simply put it in the place of omega multiply by t in the equation and in the second question d= 2 cm so the piston will be 2 cm above AB but in this case it has travelled all the way to CD and back towards AB

 

[hm12]

Thank you for solving but I din't get it properly. Aren't we supposed to use the equation:
Vout=(R2/R1+R2)*Vin

Can you please clearly mention the formula that you used and moreover where did that 100 kilo ohm came from ?

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

 

[hm12]

thank you! so negative gradient of B graph is induced E (similar to electric field strength being negative potential gradient huh?) how about the one i posted earlier than that?? (in the same page (75th)

Emf is the negative gradient of a flux time graph, magnetic flux density time graph and current time graph. Follow this and u can draw the other graphs too

 

[hm12]

Thanks for replying.. but can u plss tell me how did u find the original no. of undecayed nulei and how can u say 9 decayedinto Iron and 1 was left as manganese ?? if u dun mind then can u plss explain me in detail..

because the question says the ratio of iron/manganese is 9/1 so 9 decayed into iron and one was left total 9+1=10

 

[namename]

Emf is the negative gradient of a flux time graph, magnetic flux density time graph and current time graph. Follow this and u can draw the other graphs too

meaning that I/t,Φ/t and B/t are identical?
So does that give rise to phase difference of 90 degrees between I/t or Φ/t or B/t and Emf/t graph?

 

[m_tayyeb7]

hello can anyone help me out with (may/june 2007 Q3) how to find the area in this question???

 

[hm12]

meaning that I/t,Φ/t and B/t are identical?
So does that give rise to phase difference of 90 degrees between I/t or Φ/t or B/t and Emf/t graph?

yes they are all identical because emf=-delta Φ/t
yes there is a phase angle difference of 90 degrees

 

[Aahliya]

because the question says the ratio of iron/manganese is 9/1 so 9 decayed into iron and one was left total 9+1=10

Thanks for ur kind help..

 

[Aahliya]

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

 

[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.