Recent content by Dadface

I would have liked to edit the above post by re writing the first sentence but was unable to do so. I guess there is a time limit for editing. The following is what I would have written. Mr T, I think we wouldn't be having this conversation if the wording of the question was more specific.

Mister T, I don't think we would be having this conversation if the wording of the question was more specific. I suspect that a lot of peoples initial reaction on reading the question is that it requires one to find the minimum force needed to move the block along the surface. If that were the...

We seem agree on this point. If its understood that the minimum force cannot be bigger than mg no other FBD is needed. Even if there were students who didn't know about μ they could still come to the right response by looking at the four given equations. By doing so they should realize that μ...

Using the shortcut method requires a knowledge that the minimum force needed to just lift the mass is equal to mg. Students could illustrate that with a force diagram but I can't see any advantage in doing so. The line of reasoning involves looking at the four equations given and seeing that...

Those topics would be on the syllabus of any exam board that sets the question so, ideally, students should have a good working knowledge of them. But look at answers 1,2 and 3 given in post 15. If μ is bigger than one, each of the three answers would give a minimum force bigger than mg, in...

True, but although it can be more interesting and educationally beneficial to carry out a proper analysis the majority of students who go along that route for problems of this type would probably run out of time and end up looking at the question again or taking a guess.

If a question of this type was set in a UK multiple choice exam the examiners would expect the students to come up with an answer in an average time of just over one minute. In other words they would expect the students to reach the answer without going through a time consuming analysis of the...

The capacitance of any system can be described by the equation: C= εf In this equation f stands for a function that depends on the geometry of the capacitor or conductor. For example with a charged sphere of radius r the capacitance is given by: C = 4πεr Looking at the equations this way shows...

Agreed.

https://www.physicsforums.com/attachments/298157 The schematic I posted is basically the same as the schematic in Kim etal's paper ( Arxiv version) but is slightly more detailed in that idler photons from both semi silvered mirrors a can be detected.

I think it might help if the type of experiment fluidfcs seemed to refer to was discussed. There's a big choice of experiments including the very famous one one carried out by Kim et al. Patrick Edwin Moran prepared a nice schematic of the apparatus used and I think this is a good representation...

I think a good reply to your question has been given by ZapperZ in post 17.

Yes I had another look at his post and I see what you mean. It seems that he forgot to take into account the fact that during a transition to the ground state the ionisation energy is radiated to the surroundings.

Of course the choice of convention makes no difference to the calculations. I never said it did. But it can be confusing whatever convention is used. Some people may look at the chosen values and think they are absolute values.

Use a different convention, let the potential energy at infinity be equal to X. We can write energy equations for the particles at infinity and at the ground state. Infinity P.E. = X , K.E = 0 Bohr radius P.E. = X -27.2 ,K.E = +13.6, Energy lost = 13.6 Whatever convention is used...