1. Not finding help here? Sign up for a free 30min 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!

Finding the speed of the bob?

  1. Dec 14, 2014 #1
    1.) The problem statement, all variables and given/known data
    A(n) 2.71 m long pendulum is released from rest when the support string is at an angle of 35.8◦ with the vertical.
    The acceleration of gravity is 9.8 m/s2 . What is the speed of the bob at the bottom of the swing?
    Answer in units of m/s

    2.) Relevant equations
    Not sure

    3.) The attempt at a solution
    I tried to do 2.71sin(35.8) and I got 1.585. It's not the right answer. I also tried to do do cos(35.8) but that did not work either. Are there any other equations I have to use to find the speed of the bob?
     
  2. jcsd
  3. Dec 14, 2014 #2

    gneill

    User Avatar

    Staff: Mentor

    Where does the energy come from that results in the bob having a velocity?
     
  4. Dec 14, 2014 #3
    Does the energy come from the string?
     
  5. Dec 14, 2014 #4
    The best way to solve is to draw a neat diagram and show all the forces acting on the object. This might seem trivial but helps in better understanding of many concepts of physics.
     
  6. Dec 14, 2014 #5

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    What would the result of that calculation represent? What would its units be?
     
  7. Dec 15, 2014 #6
    since 2.71 is m I assume it would be m as well not m/s.
     
  8. Dec 15, 2014 #7

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Right, so it is not a speed.
    What do you know about potential and kinetic energy? Any equations you know of?
     
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: Finding the speed of the bob?
Loading...