Physics p4 nov 10

[ammarelahi]

please help me with p4 n10 q2 part (b) iii

 

[ammarelahi]

*p41

 

[ammarelahi]

anybody ???

 

[ohwellOK]

Since ideal gas has no intermolecular force, there is no potential energy. Internal energy is the sum of kinetic energy and potential energy. Hence, increase in internal energy will directly affect the kinetic energy. Conclusion, increase in KE = increase in temperature.

 

[ammarelahi]

nt (a) iii (b) iii

 

[ohwellOK]

Sorry my bad. You must understand first law of thermodynamics in order for you to do this question. Total internal energy = Heat supplied + Work done on gas. From P to Q, the volume of gas decreases which means work done on gas. So, the value must be positive. Work done from P to Q is 240J and the heat supplied is -600J. So the total increase in internal energy is -360J. For Q to R, the increase in internal energy is 720J.
From R to P, do you notice that it goes back to P? Since volume increases, it is work done by gas or a.k.a. negative work done. The increase in internal energy can be directly calculated from increase of internal energy you obtained for the 2 questions just now. From P to Q, it is -360J and Q to R it is 720J. If you add up both the internal energy, you will get increase in internal energy of R to P since it is going back towards the starting point. The increase in internal energy of R to P should be equal to 360J. Hence, the work done on gas is -120J. The negative sign denotes the work done by gas since the volume of gas is expanding.

I explained this by what i understand from law of thermodynamics. If there's mistake anywhere, please do not hesitate to correct me.

 

[ammarelahi]

ok. but check the mark scheme it shows completely different values for heat supplied. whats up with that !!!

 

[ohwellOK]

Yeah, most likely its a misprint.

 

[WellWIshER]

Cn SOME 1 XPLAIN JUNE 09 42 D ultrasound question last part

 

[ohwellOK]

For that ultrasound question, have you gotten the answer for b)i and ii) ? I suppose you can do these 2 questions by yourself. For the 3rd question, they are asking for intensity of ultrasound thats reflected back to the surface of the muscle. You have to times twice the fraction of the incident intensity that is transmitted from the surface of the muscle to the surface of the bone because the reflected ultrasound in between muscle and bone boundary will then pass through surface of the muscle. This will actually causes the reflected wave to be smaller in value. I've attached a image just in case you don't understand what I've just wrote.

 

[WellWIshER]

dude sorry i still didnt get it i dont get wts da meaning of fraction of da intensity!!

 

[ohwellOK]

How much is being transmitted into the medium is caused by fraction of the intensity. For instance, lets say the fraction in our bone is 5/7 and the incident wave intensity is I. The amount of ultrasound transmitted into our bone will be 5I/7.

 

[ammarelahi]

Please tell n10 p43 q3 !!!

 

[ohwellOK]

Which question of q3?

 

[ammarelahi]

part a (i) (ii) and part b (i) (ii)

 

[ammarelahi]

somebody help !!

 

[ohwellOK]

Question a (i)
They are asking for lowest point and highest point. This is SHM. According to the equation given, [ d = – 4.0 cos(220t ) ], 4.0 is the amplitude.
Formula for SHM is [ x = x1 sin wt ] where x1 is the amplitude.

Question a (ii)
According to the equation, w is 220. Number of oscillation per second is the same as frequency. W = 2pi times f.

I'm sorry I'm not able to help you with part b.

 

[filza94]

FOR Chemistry PAPER 33!!!!!!!!!!

hydrated ammonim salt titrated with KMnO4
usual salt analysis
one thermal question

We have to titrate ammonium nitrate with KMn04 or would we need to oxidize potassium iodide in the presence of ammonium nitrate and then titrate the resulting solution with sodium thiosulphate? :|

see question no.1 in june2008-31
a similar question is expected!


FOR PHYSICS ASLEVEL PAPER 33

what we hav been practicing is the electricity one with beads in place of resistors.its very simple..and ya in the oscillation one we will be having a cylinder instead of a pendulam bob..

i doubt anything concerning magnets or diodes on A2 level will come for As practicals, hmm, they might just be giving diode as just another component of the circuit system, in past years there were things like that, but the procedure is still the same, you will just have to either measure current, volt etc. and draw the graph, and by the way it will be helpful to review the graphs for diodes. before going for exam.

YOU WILL NEED
1.retort stand.
2.bob/cylinder
3.stopwatch.
4.thread
5.multimeters
6.batteries
7.clamps.
8.resistors.
9.contacts

 

[ammarelahi]

part b is the main problem!!! someone explain it to me

 

[ammarelahi]

anybody ????