Physics: Post your doubts here!

[Unicorn]

For question no. 15
Since the water will be equally divided in both the vessels after the tap is opened so vessel X will now have h/2 height of water and m/2 mass of water.
Due to which potential energy lost= (m/2)*(g)*(h/2).
So, final answer will be (mgh)/4. Hence no. B

ohhh i forgot about the mass that is why
thanks ^^

 

[JD REBORN]

Q 1 why is the answer C,it should be B?

 

[Unicorn]

Re: Physics Help here! Stuck somewhere?? Ask here!

I'm having a little doubt in vector components. Consider this: A trolley of weight, W, 600 N is going down a slope, which is at an angle of 30* to the horizontal. They say that the component of W down the slope is = W sin 30*. How is that? The way I'm thinking it should be W/sin 30*. I'm obviously wrong. Can anyone explain why?
Thank you.

whenever you have an inclined plane always resolve the weight like shown

now look at the angle theta between the weight and the resolved component this is corresponding to the angle of the plane which is 30

to get the horizontal component above the plane you use Wsin30 because if you re arrange the forces and take the horizontal one and place it above 600N force (which will be the hypnoteuse) and other component you get a triangle and to get that side of the triangle you have to use sin

hope it helped

 

[SkyPilotage]

Q 1 why is the answer C,it should be B?

Someone needs to revise his prefixes
nano is 10^-9 not ^-6
(3x10^8)/(600x10^-9) = C

 

[JD REBORN]

Someone needs to revise his prefixes
nano is 10^-9 not ^-6
(3x10^8)/(600x10^-9) = C

I dont understand what expression u have used,i mean u have divided speed of light with wavelength??

 

[JD REBORN]

In Q 15 why arent B and C correct,in Q30 why isnt B correct,in Q36 why cant A be correct and Q 39?

 

[SkyPilotage]

yes, speed = wavelength x frequency
question is asking for frequency i.e number of waves in one second

 

[SkyPilotage]

In Q 15 why arent B and C correct,in Q30 why isnt B correct,in Q36 why cant A be correct and Q 39?

Q15
B :- if thats the case it would go up but its in equilibrium
C:- ok but thats not the reason for upthrust

Q30
draw out the triangle and you will see. u=vcostheta but v = u/costheta.

Q36
Its a constant voltage supply. It can only supply a voltage of V

Q39
Nucleon Number of Uranium is 238
Mass of one nucleon is abbt 1.67 x10^-27
Multiply them !

 

[Hussnain]

AS PHYSICS
P2
N 05
Q 4 (b) (ii).
Q 5 (c) (ii)
Q 6 (a)
Q7 (b) (iii)
Q8 (b) (ii)

 

[JD REBORN]

Q15
B :- if thats the case it would go up but its in equilibrium
C:- ok but thats not the reason for upthrust

Q30
draw out the triangle and you will see. u=vcostheta but v = u/costheta.

Q36
Its a constant voltage supply. It can only supply a voltage of V

Q39
Nucleon Number of Uranium is 238
Mass of one nucleon is abbt 1.67 x10^-27
Multiply them !

thnx bro

 

[rodent123]

Capacitance Ratio is 1 : 2 and each capacitor can hold 6 volt max.
3 Volts 6 Volts
Total = 9 Volts maximum


formula is V= Vmaxsin(omega t)
omega= 2pie f
120pie = 2pie f
f = 120pie/2pie = 60Hz

will solve question 10 later and scan it for you


Because we are using graviatational fields in solving the question. We equate g of Earth = g of Moon with formula GM/x^2.
If you need help solving it tell me and Ill take a photo of it for you.

Thanks a lot skypilotage! in my last query what I actually don't get is k why are we not putting "Re" in the place of radius of earth, why X2? I mean why not solve it in terms of "Re". And can you also explain the table of the same paper question 2 part b part 2?

 

[SkyPilotage]

Thanks a lot skypilotage! in my last query what I actually don't get is k why are we not putting "Re" in the place of radius of earth, why X2? I mean why not solve it in terms of "Re". And can you also explain the table of the same paper question 2 part b part 2?

Because there are two values of X one which is between Earth and Moon and Second is after the moon.
Re is only the value of X between them.

 

[JD REBORN]

AS PHYSICS
P2
N 05
Q 4 (b) (ii).
Q 5 (c) (ii)
Q 6 (a)
Q7 (b) (iii)
Q8 (b) (ii)

For 5(c) ii
In order to find resultant intensity u will have to find resultant amplitude.So Amplitude of A-amplitude of B=3-2=1
Now u can use either Intensity of A i.e I or intensity of B i.e 4/9I to find resultant intensity.
6a:
Since potential of plates is unknown u have to assume Y is positive cuz then only force will be upwards which will balance the weight of the particle which is a force and acting downwards.Always remember to consider weight i.e mg when solving questions of these type.

 

[JD REBORN]

AS PHYSICS
P2
N 05
Q 4 (b) (ii).
Q 5 (c) (ii)
Q 6 (a)
Q7 (b) (iii)
Q8 (b) (ii)

For 7b(iii)
When temperature rises its resistance decreases so p.d across thermistor also decreases.Lets say the p.d across it is now 2.0 V,previously it was 2.7 V.Now in the previous part to find length of wire between M and Q u did the following step:
L=2.7 *100/4.5.Now in place of 2.7 put 2.0 and u will get a shorter L,so length of wire will be shorter.

Now 8(b)
Always remember that Ep(Gravitational potential energy) and h(height) have a linear relationship.So Ep increases as h increases and decreases as h decreases.Consider it this way:when an object is on ground it has zero height above ground so its Ep will be zero.As h increases its Ep will also increase.So in this case the line will be straight and will have a negative gradient and it will finish at h0.Also the reason for starting the line above curve Ek is because not all of the Ep is converted into Ek,some is used in overcoming air resistance.If u have studied Mechanincs 1 of Alevel then in this case:
Loss in Ep-Work done agianst resistance=Gain in Ek

 

[Hussnain]

For 5(c) ii
In order to find resultant intensity u will have to find resultant amplitude.So Amplitude of A-amplitude of B=3-2=1
Now u can use either Intensity of A i.e I or intensity of B i.e 4/9I to find resultant intensity.
6a:
Since potential of plates is unknown u have to assume Y is positive cuz then only force will be upwards which will balance the weight of the particle which is a force and acting downwards.Always remember to consider weight i.e mg when solving questions of these type.

THANK YOU

 

[hassam]

in ADC .......why having more bits reduces step height
how information is carried in an optic fiber.....ok its in the form of light....bt i can tvisualise how waht i ll speak can be carried by lkight,.....or how a football match broadcast cn be carried in the form of light

 

[JD REBORN]

THANK YOU

ur welcome

 

[JD REBORN]

In Q18 why cant D be correct?
Q)23
In Q27 why cant B be correct?
Q37
Q40

 

[SkyPilotage]

In Q18 why cant D be correct?
Q)23
In Q27 why cant B be correct?
Q37
Q40

Q18
Work lost is the unshaded area. you dont put work to unstretch a rubberband
Q23
a is max at the peaks, speed is max at the middle
Q27
wrong direction of motion, its a stationary wave. Motion of particles is reflected.
Q37
If it is drawn into 6 wires for example.
The area of one wire in Q is A/6 so Resistance of one wire is 6R since R is inv prop. to A.
So total R is 6R/6 = R i.e same Resistance as P
Q40
the nucleus with the smallest Z/M Ratio has the lowest a i.e Li ratio is the smallest ( 3/7 = 0.428 )

 

[SkyPilotage]

in ADC .......why having more bits reduces step height
how information is carried in an optic fiber.....ok its in the form of light....bt i can tvisualise how waht i ll speak can be carried by lkight,.....or how a football match broadcast cn be carried in the form of light

The electrical signal is converted to Pulses of light emitted by a laser or LED of frequency 2x10*8 MHz.
These are recieved and converted back to electrical signals,