Physics: Post your doubts here!

[darknessinme]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_1.pdf

Q. 23 and 25

23. frequency=8/50=0.16hz
Maximum speed of P=2 x 3.14 x 2 x 0.16=2.01
Max K.E.=1/2 x 0.002 x (2.01)^2=4.0mJ
B is answer.
25. d sin (theta)=nl
Equation 1: d sin 45=3l Equation 2: d sin(90)=nl
Divide Equation 1 by 2: sin 45=3/n
so n=4.2426..... and you have to round down to the nearest integer which is 4.
Answer is B.

 

[confused123]

a car travelling at a steady speed of 30 m/s along a motorway overtakes a coach travelling in the same direction at 25 m/s. how far ahead of the coach will the car be
a) 1 minute after overtaking.
b) 30 minutes after overtaking

answers a ) 300m b ) 9 km

 

[namename]

Anyone please help me with the graphs for electromagnetic induction i can't find it anywhere.
the questions are from s02 no.6 and s03 no.6

 

[confused123]

What about minima and maxima? what are those?

and when 2 waves meet, and theyy have like crest and trough meeting...
so when are stationary waves produced and when are destructive interference produced?

the fringes are also called maxima. dark fringe being called minima where destructive interference occus. i.e the path difference will be n+1/2 lambda if its minima or destructive interference taking place, path difference will be n lambda if its constructive intereference or maxima forming.

stationary waves are produced when two waves of same amplitude, frequency and wavelength are moving in opposite directions. they cancel out each others effect. no energy being transferred.

 

[namename]

please tell me the concept behind it I can't seem to find it in anywhere

 

[tom ed]

any suggestions,where to study phase difference in waves from?anyone?..

 

[Aahliya]

Can anyone help me out with this question below:


M/J 2005
Q7) The isotope Manganese-56 decays and undergoes β-particle emission to form the stable
isotope Iron-56. The half-life for this decay is 2.6 hours.
Initially, at time t = 0, a sample of Manganese-56 has a mass of 1.4 μg and there is no
Iron-56.

(c)Determine the time at which the ratio
mass of Iron-56 TO mass of Manganese-56
is equal to 9.0.

time = ................................ hours [2]

 

[confused123]

any suggestions,where to study phase difference in waves from?anyone?..

how much does one wave lags behind the other. one wave is equal to 2 pi radians. how much out of phase are two waves on a graph. use chadda's book cambridge endorsed one,
draw a graph , taking displacement on y axis and distance on x axis. draw a sin wave. the wave is 360 degree or 2 pi radians.
take points according on x- axis. take two points suppose A and B , a at start of the wave and b at the end of the wave, both being in same state of motion or at same displacement from mean position. they have a phase difference of 360 degree or 2 pi radians. just like this take any two points and read on the x axis how much they differ in radians or in degrees. this is how we calcular phase angle difference.

 

[Rabib_69]

Hey can anyone help me with this question? It's from O/N 11 52.. It says I should be varying the frequency of current in one coil to see
how the emf induced in the other coil varies. Now, a solution I suggested was to use a DC supply, and a switch attached to it. For a constant
time period say 10 seconds, I turned the switch on and off say 5 times for the first experiment. The frequency can thus be calculated by 5/10.
The same procedure is repeated with however greater number of times the switch is turned off and on for the same time period.
However, this particular solution was not suggested in the markscheme. Can anyone tell me if I will still be considered correct?

 

[Rabib_69]

Here's another one from O/N 11 43..

 

[hm12]

please tell me the concept behind it I can't seem to find it in anywhereView attachment 7062

emf is the negative gradient of the given graph

 

[elbeyon]

Can anyone explain me Q no. 38
Question: O/N 2011 Paper 12
Ans is A according to marking scheme.

 

[hm12]

Can anyone help me out with this question below:


M/J 2005
Q7) The isotope Manganese-56 decays and undergoes β-particle emission to form the stable
isotope Iron-56. The half-life for this decay is 2.6 hours.
Initially, at time t = 0, a sample of Manganese-56 has a mass of 1.4 μg and there is no
Iron-56.

(c)Determine the time at which the ratio
mass of Iron-56 TO mass of Manganese-56
is equal to 9.0.

time = ................................ hours [2]

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

 

[hm12]

Here's another one from O/N 11 43..

View attachment 7089

D=-4cos 120=2 cm so the piston will be 2cm above AB and moving upwards as it is +2cm

 

[hm12]

Can anyone explain me Q no. 38
Question: O/N 2011 Paper 12
Ans is A according to marking scheme.[/quote

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

 

[unique840]

Hey can anyone help me with this question? It's from O/N 11 52.. It says I should be varying the frequency of current in one coil to see
how the emf induced in the other coil varies. Now, a solution I suggested was to use a DC supply, and a switch attached to it. For a constant
time period say 10 seconds, I turned the switch on and off say 5 times for the first experiment. The frequency can thus be calculated by 5/10.
The same procedure is repeated with however greater number of times the switch is turned off and on for the same time period.
However, this particular solution was not suggested in the markscheme. Can anyone tell me if I will still be considered correct?View attachment 7088

i dun knw the ans to this ques but the emf is only induced when there is a change in magnetic flux. and that happens only when the current is alternating. not in dc

 

[abcde]

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

 

[Rabib_69]

i dun knw the ans to this ques but the emf is only induced when there is a change in magnetic flux. and that happens only when the current is alternating. not in dc

yes, but u can also use a DC circuit to give altrenating current if u turn the switch on and off constantly.. and that's how i had explained it..

 

[Rabib_69]

D=-4cos 120=2 cm so the piston will be 2cm above AB and moving upwards as it is +2cm

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..

 

[namename]

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)