Hard questions

What makes a PAT question hard?  Some are easy to misread, so you answer the wrong question and get no marks.  Some are puzzles that can’t be solved without a little dose of inspiration.  Some start off looking easy, but then you realise that the ‘obvious’ answer is just wrong, and that you don’t really understand what you thought you did understand.

Is there a hardest question ever asked in the PAT?  We think yes: it’s the last question in the 2012 paper.  It has all the features that make a question hard: it has one place where it is very easy to misread (we did when we first tried it); it needs three separate doses of inspiration (that’s one every eight minutes in the exam); and it starts by being genuinely easy, and suddenly turns nasty. Don’t try this question until you are really confident about mechanics, and don’t be surprised if it takes you a bit longer than the 26 minutes you would get in an exam.

Here is a list of some other hard physics questions:

2014, question 16. A question about diode protection circuits: easy if you have already it before in a text book or used it in real life, not easy otherwise.

2012, question 17.  This is a multiple choice question, but we have included a full written derivation to show why the answer is what it is.  It’s a lot of work for two marks.

2013, question 17.  Maybe not so hard, but you need to know your mechanics.

2010, question 20.  Requires a real stroke of inspiration.

.. and some hard maths questions:

2011, question 4.  Simple if you spot the trick.  A nightmare otherwise.

2011, question 11.  A puzzle with a nice solution, but it’s easy to miss it.

2012, question 6.  One approach is quick and neat.  Some other approaches that seem quite sensible end up in a mess.

2011, question 1. An easy question, but also easy to misread and lose half the marks.

What questions do you think are hard, and why?  Leave a comment below.

 

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2 thoughts on “Hard questions

  1. Problem 16/2014. Catastrophic enunciation !!! It asks about the current as a function of tension. I do not know the type of signal to expect. Than another phrase. There is no logical correlation with the previous text, because I understand I have to answer a completely different question . Then, someone tells us (in the solution) that usually the tension inside a diode is 1 V ???? What ????

    1. I agree this is a hard question too, because to answer it you have to know that there is a small “forward voltage” drop across the diode when a current is flowing through it.

      Try taking a look at the comments below the answer, and the links in them. This should help you to clarify the answer. If not, then post a question as a comment on that page.

      In the meantime, I’m adding this question to the list above. Thanks for pointing it out!

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