# Homework Help: Dynamics Homework Question:Planar Kinetics of Rigid Body: flywheel and rotating rod

1. Dec 5, 2012

### uncensored188

1. The problem statement, all variables and given/known data
The flywheel is rotating with an angular velocity of = 6.8 .
Determine the angular velocity of rod at the instant shown.
http://postimage.org/image/lfypabekb/

2. Relevant equations
(1) V_B= ω x r
(2) V_C= V_B + ω x r_C/B

3. The attempt at a solution
I do r times ω to get the velocity of B to be
-2.04i

I then plug into equation (2)

and i get (V_cx)i + (V_cy)j = -2.04i -1.5ωj

there are too many unknowns,
im guessing i have to use the length of DC and its angle somehow but i dont know how
THANK YOU

2. Dec 6, 2012

### BruceW

Re: Dynamics Homework Question:Planar Kinetics of Rigid Body: flywheel and rotating r

You have got the right value for the velocity.

Your second relevant equation is the velocity at a point in a rigid body (Vc), in terms of the velocity at some other point (Vb). But the rod is moving with respect to the flywheel, so the entire system is not one rigid body, so I don't think you can use this equation here.

Also, I think we can assume the question wants you to calculate the angular velocity of the rod around the point at which the rod is fixed. To calculate this is not very complicated. just think of the system at that particular instant in time.

3. Dec 6, 2012

### cmmcnamara

Re: Dynamics Homework Question:Planar Kinetics of Rigid Body: flywheel and rotating r

O and D are stationary points. They have no acceleration nor velocity. See if that helps