Another easy physics problem…

Many moons ago I posted an `easy’ physics problem from the Physics A-level paper I took in 1981. The examination comprised two papers in those days (and a practical exam); one paper had long questions, similar to the questions we set in university examinations these days, and the other consisted of short questions in a multiple-choice format. The question I posted was one of the latter type. I was reminded about it recently because, years on, it appears people are still trying it (and getting it wrong).

Anyway, since I’m teaching similar things to my first-year Mathematical Physics class I thought I’d put up another question from the same paper.

And here is a poll in which you may select your answer:

Comments on or criticisms of the question are welcome through the comments box…




8 Responses to “Another easy physics problem…”

  1. telescoper Says:


  2. C : Keeping the speed constant up the incline requires mgvsin(theta) and the acceleration requires an additional mva.

  3. Not a terribly well-designed question, because you can consider the situation when theta=0, at which point there’s only one answer that makes any sense. (i.e. you don’t have to be able to remember any of the relevant physics, other than that terms involving moving horizontally will not involve g, to select the right answer)

    • I would say that makes it a well–designed question. If you understand the principles in play (as you explained) you can pick out the correct answer straightaway without having to do a calculation. That’s ideal for a multiple choice paper where the questions must be dealt with rapidly.

      • Fair enough. I think if I were designing the question I’d have two answers that met this criterion of being obviously vaguely plausible.

    • C and D are both correct at theta=pi/2 but if theta=0 the only correct answer is C. Not a particularly “easy” question imho.

  4. Very strangely, I can only see the voting poll on my laptop – it does not appear on my desktop! Both running 64 bit Windows and Firefox. Any thoughts?

  5. […] week I posted a little physics problem that generated a large amount of traffic (at least by the standards of this blog), so I thought […]

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