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!

I Rotation vs Translation for elbow joint

  1. Jul 19, 2017 #1
    upload_2017-7-19_9-25-1.png

    If I were to cut the string and let the board move, I know I would get rotation. But, since the center of mass of the beam is moving as well (in a circle) could I also say that the board is translating once the string is cut?
     
  2. jcsd
  3. Jul 19, 2017 #2
    Yes.
    Assuming the beam is free to pivot about the hinge at its left end, it would both rotate and translate.
     
  4. Jul 19, 2017 #3
    So even though the beam will be tracing a large circle around the hinge (or more likely swinging back and forth) we can call this translation? My reasoning was because the center of mass of the board is moving as it swings. Is that correct?
     
  5. Jul 19, 2017 #4

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    The Centre of Mass of the board would drop and move to the left so that would be looked upon as translation. To avoid this, you would need to (appropriately) raise the elbow joint and move it to the right. Then you would have only rotation
     
  6. Jul 19, 2017 #5
    Even though not all movement vectors of the object are moving in space by the same amount in a given direction, we can still call this translation?
     
  7. Jul 19, 2017 #6

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    Why not? The translation doesn't need to be in a straight line or in a chosen direction. We are talking in terms of translation of the CM.
     
  8. Jul 20, 2017 #7

    A.T.

    User Avatar
    Science Advisor
    Gold Member

    Yes, you can decompose the same motion into rotation and translation in different ways.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted