# Homework H.3.C

Discussion

Shown above is the motion of the mechanism as seen by a fixed observer.

For the same motion, the above animation shows the view of an observer that is attached to the slotted link.

It is suggested that you employ the view of the observer on the slotted arm in your analysis.

## 10 thoughts on “Homework H.3.C”

1. eaaltone says:

Since bar BE is going to move off of the x axis in the next instant, does a separate axis have to be constructed to measure ddot and ddoubledot?

1. Qianyu Zhao says:

No. All given/sought are with respect to position shown in current instant.

2. CMK says:

eaaltone: In solving these problems using a moving reference frame, it is important to define not only your observer but also the coordinate axes. Here, in this problem, it is recommended that you choose the observer to be attached to BE, as well as the xyz axes to be attached to BE.

2. Ethan Chu says:

What terms are we allowed to leave in the answer?

1. Qianyu Zhao says:

Any terms that have been given in the problem statement or on figure.

3. Trevor George Hylen says:

Can we use all given values in the diagram for the answer?

4. Anonymous says:

I am having trouble starting this problem, would a rigid body velocity equation between D and A be a good way to start?

1. CMK says:

Yes, that is a good place to start. Then, follow up that with the MRF velocity equation relating the velocity of D to the velocity of A. This gives you two velocity equations for point D. Equate these two, and break into x- and y-components. Two equations for the unknowns of omega_BE and d_dot.

Repeat the process for accelerations.

5. Flynn Botkin says:

How do we determine the direction of d_ddot? It makes sense to me that d_dot must be in the negative x direction when the axes are fixed to BE, but I'm not sure how to find the direction of d_ddot.