Recent content by henryc09

Almost right, the air resistance isn't the resultant force. The resultant force is the air resistance + the weight. When the air resistance is equal to the weight, the resultant force is zero and so there is no acceleration.

Yeah, so you have 31.8 N up, and 33.42 N down, so what is the net force?

Momentum is conserved, i.e. for any process, the total momentum before = the total momentum afterwards. Basically the woman and skateboard can be considered as one object moving with speed v after she has jumped on, whose total momentum must be the same as the momentum before (of the two objects...

Problem looks like units, assuming you were supposed to give your answer in Newtons. If you want the force in Newtons, you need the mass to be given in kg.

The best way to see this (IMO) is this: If you accept (or look up a proof) that rotational K.E. is given by 0.5Iω^{2}, and that T = I dw/dt. If you think about the change in rotational K.E. : d(0.5Iω^{2})/dt = Iω dw/dt = Tω

The principle states that no two identical fermions in a system can be in the same quantum state, but what I don't fully understand is how you define a "system". For example when you apply statistical thermodynamics to a gas of non-interacting fermions you say that a maximum of one can occupy...

I see, thanks very much this is a lot clearer now.

Thanks very much. Is there a way you could explain the justification for using the rest frame of the CMB?

Hi, I've just been wondering about something so if anyone coudl explain it that'd be great. You often come across the statement that we believe the universe to be 13.7 billion years old, but I was wondering how this calculation is made? My main problem is that I'm confused as to whether every...

Homework Statement A system of 10 oscillators, characterised by a \beta^ parameter of ln(3/2) is in equilibrium with a heat bath. Determine the probability that the system should possesses Q quanta.Homework Equations p(Q) proportional to e^(-Beta*Q)The Attempt at a Solution I have seen a...

actually looking at the problem the best thing to do I think is to evaluate how far they've both moved from tom's initial position after 20s (because at this point they're both traveling with constant velocity). Then work out their velocities at this time, and from that you can easily work out...

For a) you could try to work out the position of tom and jane (relative to tom's start position) as a function of time and then find how long it takes jane to reach the end (375m) and compare this to how long it takes tom. for (b) just consider the vertical velocity, which is initially 0 and...

I don't have the Blundell book, and I haven't got that far yet no. I think I've figured this out though, but again confirmation would be good: work will be the same as \DeltaSgas is the same therefore \DeltaQ is the same. As T is constant \DeltaE is 0 so \DeltaQ=-\DeltaW as before.

Homework Statement (a) A piston is used to compress an ideal gas quasistatically from volume Vi to volume Vf . If the gas is in thermal contact with a heat bath at temperature T, such that the compression is carried out isothermally, calculate the work done on the gas, the change in entropy of...

I think something you need to get your head around is that there is nothing fundamentally that you can measure velocities with respect to. On Earth we tend to measure velocities w.r.t the earth, but when you consider the universe as a whole there is nothing you can do this with. It therefore...