# Relative velocities of rigid bodies

1. Oct 29, 2007

### kdm06

1. The problem statement, all variables and given/known data

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.

2. Relevant equations

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

3. 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: Oct 30, 2007
2. Oct 30, 2007

### Shooting Star

Where's the diagram?

3. Oct 30, 2007

### saket

ya.. plz if diagram is to be provided.. do not omit it.