Relative velocities of rigid bodies

Click For Summary
The discussion revolves around determining the velocities and angular velocity of a triangular body undergoing rotation. Given the angles and rotation rates, the equations for relative velocities are applied, specifically vB = vE + w x rB/E and vB = vA + w x rB/A. The user successfully calculates vB as -10i but struggles with the next steps, particularly in deciding whether to use theta_dot or a different angular velocity for the link AD. The absence of a diagram is noted as a significant barrier to understanding the problem fully. Clarity on the angular velocities and the need for visual aids is emphasized for solving the problem effectively.
kdm06
Messages
14
Reaction score
0

Homework Statement



A triangular body changes orientation as the suspporting links rotate. At the moment shown, theta = 90 deg, theta_dot = 5 rad/s, and beta = 45 deg. Determine vA and the angular velocity of the triangular body.
rB/C = 2j cm and rB/A = 5i cm

Points E and D are fixed. theta is the angle made between horizontal and BE. beta is angle made between horizontal and AD.

Homework Equations



vB = vE + w x rB/E
vB = vA + w x rB/A

The Attempt at a Solution



vB=vE + w x rB/E
vB=0 + 5k x 2[]j[/b]
vB=-10i

vB=vA + w x rB/A
-10i = vA + w x 5j


I am stuck at this point because I am not sure if I should use theta_dot for this w because AD is at a different angle (beta). And if I do need to use a different w (which would be beta_dot how would I find it without knowing the length of AD.
 
Last edited:
Physics news on Phys.org
Where's the diagram?
 
Shooting star said:
Where's the diagram?

ya.. please if diagram is to be provided.. do not omit it.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

Replies
9
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
4K
Replies
2
Views
3K
  • · Replies 3 ·
Replies
3
Views
6K
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K