1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A lamp hanging on from the ceiling, Im scared is going to fall on me!

  1. Nov 11, 2013 #1
    hello, Im new to this forum (so bear with me)

    I've got a lamp on the ceiling of my kitchen, its got a particular setup that Ill try to reproduce

    -----------------extra chain------------------chain with lamp attached

    ---------------------------me cooking delicious food terrified the glass lamp is going to fall on my pretty face and deform me like horrible universal monster---------------------

    so the deal is, the lamp used to hang lower, meaning there was like 15 inches of chain between the lamp and the main hook nailed to the celing. Now because Im gorgeous and tall Ive decided to raise the lamp higher so the light can illuminate further. I know, I know, its an awesome idea, how do I come up with these ideas by myself? I truly dont know, its just inspiration, magic if you want.

    Now the lamp is very close to the ceiling and very high, Ive had to move the extra chain to the secondary hook. My questions are:

    1/ if you can visualize the setup, is now the main hook bearing more weight than before now that the lamp is closer to the hook, therefore is the hook in danger of separating from the ceiling and falling into my head, or my cats heads (big surprise but Im single and live with cats, what a catch! Im open to offers clever ladies)

    2/ which formula would you apply to calculate this

    3/ finally this is the drawing of the situation (you can keep it, its my way of giving something back to humanity)

  2. jcsd
  3. Nov 11, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper

    hello headlesschicke welcome to pf! :smile:
    no, the hook is bearing less weight than before

    it is now bearing the whole weight of the lamp, and the weight of that short piece of chain, and half the weight of the rest of the chain

    (before, it was bearing the whole weight of the rest of the chain)

    i assume you are thinking that the higher the lamp is, the more force the hook must be doing to keep it there …

    no, you did the work to get it there, the hook only has to use the force to keep it there, and the keeping force is the same at any height :wink:
  4. Nov 11, 2013 #3
    thanks for the answer and for not taking the piss out of my poorly formulated and pretty obvious question

    which formula would you apply in this case? or what physics principle?
  5. Nov 11, 2013 #4


    User Avatar

    Staff: Mentor

    The main difference in the setup now is that, should the main hook let go, the secondary hook should tend to swing the falling lamp away from that pipe-cleaner figure directly below, until a point where the secondary hook, too, lets go. :smile:

    The lamp's power cord will play a part during that sequence, but not much can be foretold as the placement of the cord has not been shown in your blueprint.

    One consolation will be that, after the power cord separates, you won't see what hit you. :biggrin:
  6. Nov 11, 2013 #5
    blueprint?... oh yes, definitely my highly accurate and precise blueprint drawn with ms paint. to be honest I dont know where the lamp cord is... in fact now that you mention it.... god thats weird, where the heck is the power cord? Im going to send a furry messenger to investigate the matter further. you know whats sad? that I didnt even think about it. thats sad and Im not even joking

    always wanted to go doing the thing I most enjoy, washing the dishes. Some of us are truly privileged

    on the other hand if theres no power cord could I be anticipating a slow and painful death?, which is how I always envisioned my ending. That and with my pants down, for some reason (probably to take away the last drop of semi dignity I may have by that point)
  7. Nov 12, 2013 #6


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member


    Force = mass * acceleration

    You have reduced the mass hanging from the main hook. Some is now supported by the other hook.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook