Edexcel A Level Physics Advanced Physics II 9PH0 02 - 6th June 2024 [Exam Chat]

surely there'll be a derivation question for the kinetic theory model. its such a chunky derivation and its never been tested

Yeah, I've considered that. However, I feel like sometimes there are just certain questions that will never be asked. As if they have an idea of a topic and maybe realise that people won't learn it or something and so just decide not to bother with it until a new syllabus comes around and it's gone. Just my thoughts but it is definitely possible considering they've done a derviation for a=v²/r worth 5 marks in the past.

Yeah, I've considered that. However, I feel like sometimes there are just certain questions that will never be asked. As if they have an idea of a topic and maybe realise that people won't learn it or something and so just decide not to bother with it until a new syllabus comes around and it's gone. Just my thoughts but it is definitely possible considering they've done a derviation for a=v²/r worth 5 marks in the past.

That won't be in paper 2 since it's further mechanics which is in paper 1

surely there'll be a derivation question for the kinetic theory model. its such a chunky derivation and its never been tested

It came up in a sample paper pretty sure (if you are talking about the Pv=1/3Nmc^2 one)

Much more complicated than that 😆.
It is the derivation for rmspeed of molecules hitting the sides of a cube. With more added tenaciousness.

Yes I’m pretty sure that is the one. It was simplified in the sample paper in which all the assumptions were given but you had to derive it.

Have you got the A level Edexcel Physics Revision Guide by CGP? It has a purple and black cover. If you do, I refer you to page 136, Thermodynamics, Kinetic Theory and Internal Energy. Derive Pressure of an Ideal Gas. It involves a cube with a molecule, Q, that moves towards a wall, A with mass, m and velocity u. Its momentum approaching the wall is mu and it rebounds with momentum -mu. Change in momentum is -mu-mu = -2mu. Time between collision of Q and wall A is t=2l/u so number of Collisions per sec is u/2l. Rate of change of momentum is -2mu × u/2l = -mu²/l. Since there are many molecules the force F = m(u1²+u2²+u3²+...)/l and so Define <u²> = (u1²+u2²+...)/N for mean square speed. Then F=Nm<u²>/l. P=F/A = Nm<u²>/V, then consider 3 dimentions so x,y and z direction (this previously was all just x direction) so pythag and Define <c²> = <u²> + <w²> + <v²> . since random <u²>=<v²>=<w²> so <u²> = <c²>/3. HENCE pV = 1/3Nm<c²>.

Took like 10 mins to write all of that 😆. So was that the question in the Sample paper?

we're all doing an unofficial mark scheme tomorrow yeah?

So how was you meant to do the hot air balloon question