Archive for mechanics

Yet another easy physics problem…

Posted in Cute Problems with tags , , , on December 2, 2019 by telescoper

Last 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 I’d try another one.

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. This question is one of the latter. Incientally, for those of you who have asked, the multiple-choice examination contained 50 such questions to be answered in 2½ hours, which is three minutes per question.

(You can assume that the acceleration due to gravity is 9.8 ms-2.)

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…

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Another easy physics problem…

Posted in Cute Problems, The Universe and Stuff with tags , , , on November 26, 2019 by telescoper

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…

 

 

 

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Topical Mechanics Problems

Posted in Politics, The Universe and Stuff with tags , , , on October 6, 2019 by telescoper

In writing the homework problems for my first-year Mathematical Physics module I was sorely tempted to include some political references but I restrained myself in order not to cause any offence. That doesn’t stop me posting some examples here, however, so here are three examples of the sort of thing I had in mind:

  1. Arlene and Boris arrange to have a secret meeting near the Irish British Border. Arlene drives a car at 20 mph along a straight road that takes her within one mile of a customs post where Boris is waiting. Boris has a bicycle on which his top speed is 12 mph and he wishes to leave the customs post at the last possible minute to intercept Arlene. How far away is Arlene when Boris leaves the customs post, and how far must Boris cycle to meet her?
  2. Donald falls 200m from the top floor of Trump Tower. Neglecting air resistance, what is Donald’s velocity when he hits the ground? Assuming he has a mass of 200 kg and he is brought to rest by the impact, what is the energy dissipated? Is this likely to cause serious damage (to the sidewalk)?
  3. Jacob is reclining on a bench in the House of Commons with his head against an arm rest. The coefficient of static friction between Jacob and the armrest is 0.3 and between Jacob and the seat it is 0.4. Assuming that Jacob is infinitely thin, one-dimensional and entirely rigid, calculate the minimum angle he can make with the bench without slipping.

You may wish to refer to Fig 1 and Fig 2 here.

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An easy physics problem…

Posted in Cute Problems with tags , , , on May 26, 2011 by telescoper

Based on the popularity of something I posted last week, I thought some of you might find this little problem amusing. It’s from a 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 was short questions in a multiple-choice format. This is one of the latter type, from the mechanics section.

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

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