ALL CIE PHYSICS DOUBTS HERE !!!

[AN10]

O/N 10 P43 q10 (b)
O/N 10 P41  q2 (b) iii
anyone plz help

[Sue T]

from ppr 43 ques10b you have 2 situations - open switch and closed switch - ive attached an expalanation

[cashem'up]

hey a question from the new CIE Physics Book - Exam - style question(they dont have answers)

1.A hot air balloon its basket and passengers have a total mass of 450kg. The inflated balloon holds 3000m^3 of air.
(a) minimum forced needed to lift balloon of the ground? - 4500 N
(b) Atm pressure is 1.03 x 10^5 abd density of air is 1.23kg/m^3
(i) calculate mass of 3000m^3 air? - 3690kg
(ii) Calculate Number of Moles in the balloon, Consider air relative Mr as 29 ? 1.27 x 10^5 mol

THIS IS PRIOR INFORMATION AND CALCULATIONS DONE BY ME..the next two parts i dont
know

c. As the air is heated some of it is expelled through a vent at the top of the balloon. Calculate max mass of air that can remain in balloon to give sufficient upthrust for the balloon to just the leave the ground? DONT KNOW

d. Calculate the minimum temperature of the air inside the balloon for the balloon to just lift off the ground??? DONT KNOW

[physichemaths]

Help me with nov 08 question 10 part b?

[aldehyde1612]

from ppr 43 ques10b you have 2 situations - open switch and closed switch - ive attached an expalanation

When V- is more than V+ ... isnt the output negative??
Vout= G x [V+ - V-] .. so if V- is 3V and V+ is 2V, then  2-3 = -1 .. So Vout is G x -1, which is negative?
And vice versa when V+ is more than V- ??
Thats the logic we were taught, but then with the marking scheme that logics wrong.. so can you please explain?? 

[Sue T]

humans make marking schemes - it can be wrong you no - cuz ryt in front of me in the booklet the rule is set and an xample is done - so yes wat i said is the ryt one - i asked my teacher also

[Sue T]

Help me with nov 08 question 10 part b?

so you have : V_out/V_in = R_feedback/R₁
so at 100kohms calculate the R_feedback using the fact that the LDR is in parallel to the 50kohm resistor
so 1/50k + 1/100k = R_feedback
once you get R_feedback just substitute the values and obtain V_out
the second part uses the same method

[aldehyde1612]

humans make marking schemes - it can be wrong you no - cuz ryt in front of me in the booklet the rule is set and an xample is done - so yes wat i said is the ryt one - i asked my teacher also

I was saying you're explanation agrees with the marking scheme... but me and all my physics teachers got it the other way around (the way I said). 
But true. humans do make mistakes.
Thanks for the help.

[Dthdfyng]

Hey everyone! i really need some help with Physics P4 past paper questions

O/N 05 (Q5)(ii) and (Q6)(c)(ii)
M/J 06 (Q3)(a) and (Q6)(c) and (Q7)(c)
O/N 06 (Q7)(b)
M/J 10 (Q3)(b) and (Q9)(a)(ii)
O/N  10 (Q8)(c) and (Q11)(b)

will appreciate any help!

[Master_Key]

Hey everyone! i really need some help with Physics P4 past paper questions

O/N 05 (Q5)(ii) and (Q6)(c)(ii)
M/J 06 (Q3)(a) and (Q6)(c) and (Q7)(c)
O/N 06 (Q7)(b)
M/J 10 (Q3)(b) and (Q9)(a)(ii)
O/N  10 (Q8)(c) and (Q11)(b)

will appreciate any help!

O/N 05 (Q5)(b)(ii)

1. v is small so deflection is larger.
2. More force = More deflection.

[Master_Key]

Hey everyone! i really need some help with Physics P4 past paper questions

O/N 05 (Q5)(ii) and (Q6)(c)(ii)
M/J 06 (Q3)(a) and (Q6)(c) and (Q7)(c)
O/N 06 (Q7)(b)
M/J 10 (Q3)(b) and (Q9)(a)(ii)
O/N  10 (Q8)(c) and (Q11)(b)

will appreciate any help!

M/J 06 (Q3)(a)
The gradient is sensitivity. It is not linear and varies with temperature.

[Sue T]

I was saying you're explanation agrees with the marking scheme... but me and all my physics teachers got it the other way around (the way I said). 
But true. humans do make mistakes.
Thanks for the help.

hey lsn - i meant the markin scheme is rong - i typed it out wen i ws sleepy - i mixed it up - jus switch tht part round - so bottom line if v- is more it becomes negative - sorry 4 th confusion - i ws bout 2 go 2 bed :p

[da_rockstar]

Guys i had a question i wanted to ask.
if you have 2 capacitors in series together. you obviously say that the charge on each is the same right?
so when you take their energy individually and on the other hand take their combined energy...won't the two values differ. i mean the combined energy will fall according to the formula of Q^2/2C. that will give a reduced overall energy compared to what you have from the individuals because your capacitance decreases in series.

and in one question i saw that while calculating individual energies of the capacitances they reduced the charge on them by 2. that is divided the charge that you get through their combined charge to give charge on one of the capacitance. but that confused me greatly since in my opinion the charges across them both should remain the same. please do let me know where i'm wrong in my assumptions. reply asap please Thanks in advance

[Sue T]

Guys i had a question i wanted to ask.
if you have 2 capacitors in series together. you obviously say that the charge on each is the same right?
so when you take their energy individually and on the other hand take their combined energy...won't the two values differ. i mean the combined energy will fall according to the formula of Q^2/2C. that will give a reduced overall energy compared to what you have from the individuals because your capacitance decreases in series.

and in one question i saw that while calculating individual energies of the capacitances they reduced the charge on them by 2. that is divided the charge that you get through their combined charge to give charge on one of the capacitance. but that confused me greatly since in my opinion the charges across them both should remain the same. please do let me know where i'm wrong in my assumptions. reply asap please Thanks in advance

it'll be hard 2 really answer ur ques without an example - so if u could find that ques i can c wat i can do -- but anyways in terms of energy the thing is when capacitors are in series, the charge is Q for both thats ryt - but the potential is shared. When in parallel the charge is shared, but the voltage is same. E=Q²/2C can only be used in certain situations... like amm...ugh u have 2 gimme an example... :s

[your sister]

1. graph of gravitational potential and radius : gradient gives gravitational field strength

2. graph of gravitational force and radius : gradient gives gravitational field strength


which one is correct 1 or 2 ??