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!

Homework Help: Can someone please check this modified pendulum velocity problem

  1. Dec 22, 2009 #1
    [solved] Can someone please check this modified pendulum velocity problem

    1. The problem statement, all variables and given/known data
    I'm looking for the ballistic pendulum velocity for a simple machine (pull back lever, it shoots a marble into a block that raises to a certain degree measured)

    I have the angle that the block is raised
    length of the string
    mass of block


    2. Relevant equations
    Ke=Pe (1/2MV^2=MGH)
    cos@=length of sting - height/length of string






    3. The attempt at a solution


    .20cos25.3 = .20 - h

    which gives me .02cm, which in turn gives me .6m/s, which seems a bit slow, I feel as if I'm messing up my trig but I don't know where...




    s.jpg

    I figured out I was using an incorrect derivation, I was just so fixed on thinking I had messed up my trig work
     
    Last edited: Dec 22, 2009
  2. jcsd
  3. Dec 22, 2009 #2
    I'm confused in what you want us to check? What specific quantity are you concerned about?

    The intial velocity of the object after its pulled back a certain distance?
     
  4. Dec 22, 2009 #3
    I've been given the manufacturers velocity, which is 5.5m/s, I'm getting less than 1m/s and honestly I don't see what I'm doing wrong.
    BTW here is the pendulum I used:
    1600-4.jpg
     
  5. Dec 22, 2009 #4
    What exactly is this:

    V = Rad(9.8 * 0.2)/0.5

    ?
     
  6. Dec 22, 2009 #5

    Ke=Pe
    1/2mv^2=mgh
    masses cancel, divide both sides by .5
    take the square root of both sides to get v=rad(GH)/.5
     
  7. Dec 22, 2009 #6
    Just your notation--rad is confused with radians. [tex]\sqrt{}[/tex] is available on the latex option on advanced setting with the icon:[tex]\Sigma[/tex] Or simply denote as sqrt(gh/.5)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook