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Physics Job interview physics question examples?

  1. Sep 23, 2011 #1
    Hi all :-)
    A little while back I went for an interview for a physics based job which, unfortunately, I completely screwed up. Part of the problem was that when they asked me some really basic physics questions, the sort of thing I haven't done since first/second year, I was a.) put off because I wasn't expecting them, and b.) I'd had so little recent practice at them I couldn't really implement the right sort of lateral thinking, etc. So basically, I need to practice them.

    An example would be how to measure the speed of a bullet using only a ruler (though that's one that I did get right, using suvat equations, etc).

    I was wondering if people could either post examples I could practice on, or post links to practice problems?

    Many thanks in advance :-)
    Last edited: Sep 23, 2011
  2. jcsd
  3. Sep 23, 2011 #2


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    I thknk you have slightly missed the point here. I expect they were not trying to ask you the sort of questions that you can "practice". They were trying to find out whether you can think on your feet.

    Speaking as an interviewer, we have a large collection of this type of question, and if the interviewee appears to "know the right answer" to one question we just switch to a different topic, till we find something that forces him/her to start thinking.

    We might even try to convince the interviewee that his/her right answer is actually wrong, to find out how well they defend it, or if they just roll over and accept what an "authority figure" says without challenging it.
  4. Sep 23, 2011 #3

    D H

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    You guys are mean. I just interviewed someone today who said our interview process is easy (we thought it was tough!). It made me think: Are we soft? We don't give interviewees a pad of paper and ask them to write a thirty minute essay on the management style of their last boss. (I would have walked: This company is not for me.)

    Companies are trying to accomplish a number of things in an interview, number one being "Would it be a big mistake to hire this person?" We make mistakes hiring people who
    • Won't fit in, apparently the motivation for the thirty minute writing exercise, but there are better approaches;
    • Don't know beans, which is why interviewers torture freshouts from college with silly questions such as how to measure the speed of a bullet using only a ruler. Employers typically don't offer refresher courses for subpar freshouts;
    • Aren't creative, and those silly questions serve double duty here;
    • Are flipping lazy, so we poke at what motivates you and always listen for any clues that you are plagued with this disease.
    The list of mistakes goes on and on. Those mistakes can be very, very expensive. Even a company that has never made a bad hiring mistake is very cognizant of how utterly disastrous such a mistake can be.

    Your first goal in an interview is to ensure the company you are interviewing that hiring you would not be a mistake. Your second goal in an interview is to convince the company you are interviewing that hiring you would be hugely advantageous.

    At the same time we interviewers are asking ourselves "Is hiring this person going to be a big mistake?" we also are asking ourselves "Is hiring this person going to be a big plus?" Those nasty "how to measure the speed of a bullet using only a ruler" questions serve (at least) triple duty. Do you know your basics, are you creative, can you think on your feet, are you confident in your knowledge, willing to admit when you don't know something?
  5. Sep 24, 2011 #4
    On the other hand one way of getting good at answering questions is to look at a ton of questions.
  6. Sep 24, 2011 #5
    The questions that I got in my interview was

    1) solve the harmonic field equation in 2-d
    2) write down the PDE for a diffusion equation. Using fourier transforms calculate the green function for that equation
    3) Explain QR and Choelsky matrix decompositions
    4) Calculate the integral of 1/cos(theta)
    5) Persons A and B alternatively flip a coin with probability p of getting heads. The person getting heads wins. What is the chance that person A will win the game

    Also one thing that I look for is not just if the candidate solves the problem, but how they seem to emotionally react to the problem. If you have a candidate that seems to enjoy getting doing hard math problems, this matters a lot. If you have someone that can do the problems but seems to dislike doing them, then this is going to be a problem for a job in which they are expected to do that for 12 hours a day.

    The other thing is that there is no rule that the interviewer knows the answer to the question. For example, if you quickly answer the question of how you'd measure the speed of a bullet with ruler, I'd ask how you'd measure the speed of the bullet with a dog whistle.

    I happen to have no clue what the answer to that question is since I just made it up, but I'd like to see how the interviewee responds to that question.
    Last edited: Sep 24, 2011
  7. Oct 2, 2011 #6
    Thanks for the response. That's just the think, I finished my course almost a year ago now, and I feel like I'm not used to having to think any more, and I wanted some practice questions to keep my brain active, and to get back into the kind of thinking demanded by that particular style of question. Your insights are interesting however, thanks for that.

    D H, thank you for your response, it wasn't really answering my question, but there's information in your post that I will probably find useful :-)

    Exactly :-)

    Ok, so what would be a favourable response there? I'm guessing you're assessing the person's ability to admit that they don't know something, and how they cope with that?

    On a side note, I recently saw the job that I had the interview for re-advertised, so maybe I didn't do as badly as I thought. I do know that I wasn't firing on all cylinders that day. What are your thoughts about someone applying for a job that they'd previously been rejected for?
  8. Oct 2, 2011 #7
    First, you do not want that job. The work may sound cool, but if you didn't meet their expectations, then you probably don't want to re-apply.

    Second, many large organizations have elaborate and very restrictive hiring practices created by a Human Resources specialist and a company attorney. These procedures are created under the illusion that by following them, somehow they can avoid getting sued and dragged in to court. These often result in bizarre interview questions.

    Though it wasn't on my interview, I did get a question during my probation that went like this: Given a very smooth large circular pipe with no friction, and a very small sphere (a BB) placed on the very top of the pipe with an infinitesimally small push, develop an equation that would indicate the point at which the BB departs the pipe.

    Of course, this was done for fun and it was done 25 years ago, back when most companies had a Personnel section, not a Human Resources office.

    The bottom line is that if you are offended or confounded by these questions, you're not in the right place. The companies that think such questions are a good idea are probably not where you would thrive.
  9. Oct 2, 2011 #8
    Hmm... I'm not sure that this is the case; correct me if I'm wrong, but you sound like you're from the US? I'm in the UK, I suspect that companies are a little less litigious than over there, certainly in the area of research.
    I got the impression that the people interviewing me were experienced physicists who had formulated their own questions, rather than asking things that they had been directed to.

    I'm not, like I said, I'm just a little out of practice :smile:
  10. Oct 2, 2011 #9
    That's not the situation that I've seen in any company that I've every worked for. HR gives you a list of questions that you are legally forbidden from asking (for example martial status, religion, ethnic origin etc. etc.), but they aren't involved in structuring the interview. HR isn't heavily involved in hiring people because it's really, really tough for an outsider to sue a company for hiring discrimination. Now when you have to *fire* someone, then HR and the lawyers look at you closely, and one reason companies like to lay people off in groups is that if you lay off 50 people at a time, it's possible to statistically prove non-discrimination.

    What I have seen is you have a company in which the people making the decisions don't have any technical background so that they ask people cookie cutter questions. Also, we have had situations in which we've had to use someone non-technical for a screening interviews.
  11. Oct 2, 2011 #10
    Something that you can do is to make up random questions

    How do you measure the A of B with C?

    Then randomly put words into A, B, and C.

    Probably not a good idea unless you are desperate.

    Also this is one time in which a headhunter is really, really useful because an HH can find out why you didn't get a job.
  12. Oct 4, 2011 #11
    So how'd you do? I think I'd have a problem with a couple of these during an interview.
  13. Oct 4, 2011 #12
    Miserably for the first few interviews, but I managed to do better with practice. One good thing about going to a lot of interviews is that there are only so many interview questions that you can get, and if you stick around, you'll find people repeating them.
  14. Oct 4, 2011 #13

    D H

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    Except for my first job out of college, I always set up a couple "practice interviews" with companies I would never, ever want to work for. (No matter what field you work in there are some real loser employers out there. People in the field tend to know who they are. If you don't know, ask around.) Those practice interviews served to get me into interview mode. Blow one those practice interview: No harm, no foul. I wouldn't have accepted had I impressed them enough to garner an offer.

    My goal in those practice interviews was to get that offer. Nicely telling those practice companies "no thanks" for the offer helped boost the ego in prep for the inevitable ego deflation that would come with the first "no thanks" from a non-practice interview.
  15. Oct 9, 2011 #14
    For the research lab I worked at we worried more about the candidates on a personal level than a academic level. They were phd hires, and would give a presentation about their work to a large audience of scientists which would ask related questions. Then small interviews with people, but at an informal level, no quizzing or grilling. Then we would take them to lunch to see how they get along with everyone in a really informal environment. Overall it worked out well, It's more important to get along with someone in our opinion than to see if they can integrate trig functions on their feet.
  16. Oct 9, 2011 #15


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    That's a fantastic idea! Consider it stolen :biggrin:.
  17. Oct 10, 2011 #16


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    Job interviews are an exercise in psychology - the prospective employer is testing your reasoning and communication skills. Your answers are less important than how you handle the question. There is no harm in not having an off the cuff answer so long as you ask appropriate questionsn. Your performance under pressure is what they are evaluating.
  18. Oct 19, 2011 #17
    I guess I'm just old, but remember an interview is a two way. Yes, they are looking at you, but you are looking at them too. If they got that many silly questions off, you failed to carry out the basic interview. They ask that crap when there is little else to talk about. e.g. you were boring.

    Do your homework and find out all you can about the company (origin, recent past, present, and future), what they are doing, and what they are looking at getting into. Look at stock analyst reports for projections on future growth areas for the company. Find out WHY they are hiring someone and why the someone should be you. When you get into an interview situation start out with something like "I see you are developing the XYZ, I worked in that area helping a Professor Jones in graduate school and found it very interesting. In fact, when I saw this company was working in that area, I started looking for opportunities here. I hope during the interview process I can get a chance to meet some of the team working this project." In other words, show real interest in what they are doing. Show real knowledge about what they are doing. Don’t bluff knowledge. You’re not expected to know it all, but know enough to be technical asset that is trainable in their implementation of the new technology. Direct the interview or be directed. I made that mistake once more than 30 years ago, and it's never happened again.
  19. Oct 20, 2011 #18
    What was the mistake, directing the interview or being directed in the interview?
  20. Oct 20, 2011 #19
    While you need to always be responsive to the question, sitting like a bump on a log waiting for the next zinger gets you the next zinger.

    You can't control the interview in any absolute sense. When I say "direct the interview", I mean to use the knowledge you have of the company (as suggested above) to steer the interview and show true interest in being part of the company and why. People naturally like to talk about themselves, their work, and their company, so if properly prompted, the interviewer will love to talk about those things. You need to glean from the interviewer those things they see as significant, and with that information, feed back into the conversation how you would contribute to the future of the organization. When you move on to the next interviewer in the company, use the last interview to tee up your question to the interviewer. “When I spoke with Dr. Jones he was excited about the upcoming work on the ABC project. That sounds like a very promising area, and would that be an area I could be involved in?” It shows you were listening, interested, and it gets down to the meat of the job, leaving no time for zinger development. Stay focus on the company and how they would use you.

    And, don’t BS, its frivolous and may leave a sense of lacking direction. This guy/gal isn’t your buddy yet. Make reasonable eye contact, sit up straight, and never be the first one to ask for a second drink at dinner.

    Lastly, just as every company may not want you, you may not want every company you interview with. Like shoes, you're looking for a fit. The fit may not be perfect (I have one foot 1/2 size larger than the other), so don't expect perfect.

    Yea, I’ve always been long winded ;-)
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