physics and chemistry doubts!!

[Faiza Anwar]

if u u have any question or useful information regarding these subjects' paper 1 nd 3 then post here!!

 

[DarkEclipse]

Several threads already exist regarding this. You might wanna check those out instead of posting new threads.

 

[hard_worker]

if u u have any question or useful information regarding these subjects' paper 1 nd 3 then post here!!

he's right! u better go check HUNDREDS of other threads around the same topiccc !!

 

[Faiza Anwar]

well yeah!!!

 

[Phoenix Blood]

Explain the two question-answers please...

Awesome12 eureka!

 

[Phoenix Blood]

 

[Awesome12]

View attachment 42989 View attachment 42990



Explain the two question-answers please...

Awesome12 eureka!

See if 5 V is applied, it will move by 1 cm
It is moving by 1.5 cm, so
5 : 1
x : 1.5
Find x

It takes 1.0 ms to move 1 cm HORIZANTALLY
We need to find the frequency of one cycle
Time for one wave is 4 ms (4 cm is the wavelength)
Frequency = 1 / time

Frequency = 1/4
= 0.25 Hz

 

[Phoenix Blood]

No 'C' ? Air giving k.e and all....?

 

[Phoenix Blood]

Why not 'D' ?

 

[eureka!]

View attachment 43000

No 'C' ? Air giving k.e and all....?

Remember that draughts expose more dry air for evaporation. Water from the damp cloth evaporates. And evaporation cools down a body. So the liquid contracts.

 

[Phoenix Blood]

Remember that draughts expose more dry air for evaporation. Water from the damp cloth evaporates. And evaporation cools down a body. So the liquid contracts.

But doesn't it provide k.e at the outset?

 

[eureka!]

View attachment 43001

Why not 'D' ?

Because the angle of incidence in D is 90˚ to the normal, which means it will carry on with no refraction.

 

[Phoenix Blood]

What variable of a circuit does current affect? (Voltage controls brightness.. current? )

 

[eureka!]

But doesn't it provide k.e at the outset?

Why should it? It's not hot air, so the liquid won't expand.

 

[eureka!]

View attachment 42992

You got this answer, right?

 

[Phoenix Blood]

You got this answer, right?

No, see if i'm right :

time in steel= 120/5000 = 0.024 s
time in air= 120/1500 = 0.08 s

difference= 0.056?



And see what all marking scheme says:
distance = speed × time in any form NOT speed = 2d/t
tair = 120 ÷ value for speed of sound in air
trail (= 120 / 5000) = 0.024 s
(time difference =) candidate’s tair – candidate’s trail correctly evaluated
(expect 0.400 – 0.024 = 0.376 s)

 

[eureka!]

No, see if i'm right :

time in steel= 120/5000 = 0.024 s
time in air= 120/1500 = 0.08 s

difference= 0.056?



And see what all marking scheme says:
distance = speed × time in any form NOT speed = 2d/t
tair = 120 ÷ value for speed of sound in air
trail (= 120 / 5000) = 0.024 s
(time difference =) candidate’s tair – candidate’s trail correctly evaluated
(expect 0.400 – 0.024 = 0.376 s)

The speed of sound in air is approx 33o m/s.
Time taken in air will be much more; sound travels fastest in solids.
But ecf ke marks you'll get inshaAllah, your calculations are correct.

 

[Phoenix Blood]

The speed of sound in air is approx 33o m/s.

Hell, yeahhhh! Jzk Been racking my brains, dividing, doubling, and all. Lol.

 

[Faiza Anwar]

View attachment 42989 View attachment 42990



Explain the two question-answers please...

Awesome12 eureka!

in your first question.. it is written that 5V moves the wave 1 cm upwards.. nd the wave is moving 1.5cm upwards so we will multiply 1.5 with 5.. the answers is 7.5..
in the second part.. i ms moves the 1cm horizontally.. i cycle travels 4cm so it takes 1 x 4= 4ms.. and from this u get the frequency
tell me if the answers are correct or no..

 

[Faiza Anwar]

View attachment 43001

Why not 'D' ?

the ray bends towards the normal as it enters the glass.. nd then away from normal as it enters air