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!

Oscillation question...

  1. Sep 19, 2016 #1
    • Member advised to use the homework template for posts in the homework sections of PF.
    To increase the period of oscillation of a pendulum in 1 second, it is needed to increase the length of it in 2 meters. Calculate, in seconds, of the initial period of oscillation of the pendulum.

    I found this question online a few minutes ago. I have not learned this in physics class yet so bare with me :)
    Because it is asking for the period of the oscillation I figured I would need the equation: T = 2π√(l/g)

    To set up the equation, I wrote it like this

    2π√(l/g) + 1 = 2π√(l+2/g)

    as the period of the oscillation increased by one when the length increased by 2 meters. When I solve this equation though, everything except cancels itself out, so I can't find the initial length to plug back into the equation to find the initial period... Again, I am 1 month in of my first year of physics so don't crucify me for my mistakes please (lol), and the wording on this question is quite confusing too, so I may have it all wrong but hopefully you can see where I'm going with this ;)

    Thanks in advance!
  2. jcsd
  3. Sep 19, 2016 #2

    Charles Link

    User Avatar
    Homework Helper
    Gold Member

    I think you set it up correctly. Try squaring both sides, cancelling the terms that cancel, and then grouping terms and squaring once more. If you are careful with the algebra, you should get an answer for "l". (You do need a parentheses around your (l+2).)
  4. Sep 19, 2016 #3
    I only put the parentheses around the l/g to show that it was included in the square root. Anyway, you can take a look at my work:
    Unless I messed it up, the lengths do in fact cancel each other out. :/
  5. Sep 19, 2016 #4

    Charles Link

    User Avatar
    Homework Helper
    Gold Member

    How about the 2ab term when you square the left side? ## (a+b)^2=a^2+2ab+b^2 ##.
  6. Sep 19, 2016 #5
    ohhhhh.... I completely forgot. So now when I solve the equation, I get about 3.09047 for the initial length. When I put this back into the equation T = 2π√(l/g) I got about 3.525678 seconds. Im not sure if it is correct yet but thanks a lot for the help!
  7. Sep 19, 2016 #6

    Charles Link

    User Avatar
    Homework Helper
    Gold Member

    I didn't compute an exact answer either, but that's approximately what I got. Good work !!!
  8. Sep 20, 2016 #7


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    "in 1 second" = "by 1 second" or "to 1 second"?
  9. Sep 20, 2016 #8
    The person who asked this problem meant "by." I just copied the problem down verbatim in case that wasn't the case.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Oscillation question...
  1. Oscillations question (Replies: 1)

  2. Oscillation Questions (Replies: 4)

  3. Oscillation Question (Replies: 4)

  4. Oscillator Questions (Replies: 16)

  5. Oscillation question (Replies: 6)