Physics, Chemistry and Biology: Post your doubts here!

[aditya surana]

during electrolysis of potassium sulfate, 2 gases are released.. what are they?

 

[ZainH]

during electrolysis of potassium sulfate, 2 gases are released.. what are they?

If the solution is AQUEOUS potassium sulfate then I believe oxygen and hydrogen should be released.

 

[aditya surana]

how??????? please explain..

 

[MERIHAN]

Since the critical angle is not given in the question, and it states that leaving through point Q, then it means that you have to measure the angle of incident, and reflect it with the same angle, by the use of a medium line. Do this at point Q and at point R, and then draw the middle reflections and medium lines which connect the beam together. That's it.

CAN U PLZ SHOW A ROUGH DRAWING ....... THNX IN ADVANCE !!!

WHICH ONE IS CORRECT

 

[chaotic]

how??????? please explain..

Not sure if I'm right, but because potassium is very reactive so it stays in the solution, so hydrogen is given out.
and sulphate stays in the solution (don't know the reason behind this), so oxygen is given out.

EDITED

 

[Moi]

please help anyone!
what is the difference between the motion of objects falling with and without air resistance?

Without air resistance, it falls at a constant acceleration.
With air resistance, it accelerates at the bigining until air risitance is equal to the object's weight, causing a resultant foce of zero, it'll start falling at a terminal speed (constant speed) <--- After it accelerates in the begining

 

[tribianni]

For c) Use the equation for power, but you'll have to change it a bit.

Power = energy /time
Energy = power*time
Energy = current*voltage*time
Energy = current^2*resistance*time

NOW you can calcuate it as you have the current, resistance, and time!

ENergy = 2.5^2*3*1
=18.75J

For d) it's easier, just use the formula for power involving current and voltage.
Power= current*voltage
Voltage = power/current
Voltage= 18.75/2
=7.5v

For e) You just subtract the orignial voltage from the one you calculated in part d)!
22000-7.5=21992.5V

we dont have time!!!!

 

[ThatReallyReallyWeirdDude]

please help anyone!
what is the difference between the motion of objects falling with and without air resistance?

Alright then
When any object is falling the main thing acting on it will be the weight of the object, pulling it downwards. As per Newton's second law this will cause acceleration.
When there's no air resistance the acceleration will be constant, as nothing is opposing it (this means the graph of the speed will be a straight line)
When there IS air resistance, the air resistance will act in the opposite direction as the weight, so the net force = weight-air resistance
As the speed of the object increases, so does the air resistance until the point where weight = air resistance, so net force = 0
As per newton's FIRST law, it will have a constant speed (when no force is acting on an object it will eithe rmove with a steady speed or not move etc.)
So acceleration will decrease until it is zero and speed is constant, and this speed is called the terminal velocity
The graph will be a curve where the gradient decreases until it becomes straight

 

[thats_me]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_31.pdf
10 (b)

Need help with the drawing, I don't have the text book, so that's why.

also want the formulas concerning latent heat and heat capacity, thanks.

http://www.google.com.sa/imgres?um=...i=_ke-T5ypHMyeOtb_5BM&zoom=1&biw=1366&bih=576 <--- drwing
specific heat capacity =E=mc*(temp change)
latent heat of fusion/vapourization = E=M*L

 

[ZainH]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_31.pdf
10 (b)

Need help with the drawing, I don't have the text book, so that's why.

also want the formulas concerning latent heat and heat capacity, thanks.

Formula for latent heat : Latent heat= energy/mass
Formula for specific heat capacity: Specific heat capicty= energy/ mass*(Change in temperature:Final temp-initial temp)

LOL THIS IS A TERRIBLE DRAWING I KNOW, But you have to understand I did it using a laptop mouse in under 2 mins x)

 

[chaotic]

http://www.google.com.sa/imgres?um=...i=_ke-T5ypHMyeOtb_5BM&zoom=1&biw=1366&bih=576 <--- drwing
specific heat capacity =E=mc*(temp change)
latent heat of fusion/vapourization = E=M*L

Thank you, much appreciated.

 

[ZainH]

http://www.google.com.sa/imgres?um=...i=_ke-T5ypHMyeOtb_5BM&zoom=1&biw=1366&bih=576 <--- drwing
specific heat capacity =E=mc*(temp change)
latent heat of fusion/vapourization = E=M*L

What o.o?
Both formulas are wrong, you might want to double-check your textbook...
Im confident that latent heat= energy DIVIDED by mass
and specific heat capacity as well, it is
Heat capacity=e/mass*change in temperature

 

[chaotic]

Formula for latent heat : Latent heat= energy/mass
Formula for specific heat capacity: Specific heat capicty= energy/ mass*(Change in temperature:Final temp-initial temp)

LOL THIS IS A TERRIBLE DRAWING I KNOW, But you have to understand I did it using a laptop mouse in under 2 mins x)

Doesn't matter if it's horrible, as long as it's understandable Thanks

 

[ZainH]

we dont have time!!!!

It asks how many rungs he can climb in 5 SECONDS.
The times given x)

 

[ThatReallyReallyWeirdDude]

during electrolysis of potassium sulfate, 2 gases are released.. what are they?

If it's aqueous then oxygen and hydrogen.
Sulfates are inert electrolytes.

 

[thats_me]

What o.o?
Both formulas are wrong, you might want to double-check your textbook...
Im confident that latent heat= energy DIVIDED by mass
and specific heat capacity as well, it is
Heat capacity=e/mass*change in temperature

:O noooo E=M*L

 

[ZainH]

:O noooo E=M*L

Just realized L=E/M is the same thing as E=M*L xD

 

[chaotic]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w10_qp_33.pdf

2b (i)

Need help on this

 

[thats_me]

Just realized L=E/M is the same thing as E=M*L xD

lol same here

 

[ZainH]

CAN U PLZ SHOW A ROUGH DRAWING ....... THNX IN ADVANCE !!!

WHICH ONE IS CORRECT
View attachment 10721 View attachment 10722

NEITHER! Remember the mark scheme? It said only ONE reflection, if its more then one they will cut a mark, if it's more then two then you get 0.
It's only one reflection.. I'll try to make a diagram :S