Rotation vs Translation for elbow joint

  • #1
physics gal
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?
 

Answers and Replies

  • #2
.Scott
Homework Helper
2,617
950
Yes.
Assuming the beam is free to pivot about the hinge at its left end, it would both rotate and translate.
 
  • Like
Likes sophiecentaur
  • #3
physics gal
Yes.
Assuming the beam is free to pivot about the hinge at its left end, it would both rotate and translate.
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?
 
  • #4
sophiecentaur
Science Advisor
Gold Member
25,011
4,744
Yes.
Assuming the beam is free to pivot about the hinge at its left end, it would both rotate and translate.
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
 
  • #5
physics gal
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
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?
 
  • #6
sophiecentaur
Science Advisor
Gold Member
25,011
4,744
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?
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.
 
  • #7
A.T.
Science Advisor
10,582
2,203
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?
Yes, you can decompose the same motion into rotation and translation in different ways.
 
  • Like
Likes jbriggs444 and Nidum

Related Threads on Rotation vs Translation for elbow joint

  • Last Post
Replies
4
Views
5K
Replies
3
Views
11K
Replies
0
Views
2K
Replies
9
Views
936
Replies
10
Views
6K
  • Last Post
Replies
5
Views
2K
Replies
2
Views
24K
Replies
8
Views
2K
Replies
1
Views
571
Replies
10
Views
1K
Top