# Homework H5.M - Fa22

DISCUSSION

Four-step plan

Step 1: FBD
Draw a free-body diagram particles A and B, along with the bar, altogether. Is angular momentum for this system conserved? Why, or why not?

Step 2: Kinetics - Angular impulse/momentum
Write down the angular momentum for A, B and the bar individually, and then add together. For a particle A, for example, recall that angular momentum is given by HO = m rA/O x vA.  For a rigid body, HO = IOω. You will also need the coefficient of restitution equation relating the radial (normal components here) components of velocity of A and B during impact.

Step 3: Kinematics
For writing down the velocity of points A and B, a polar description is recommended. For example, vA = R_dot eR + Rωeθ.

Step 4: Solve
Solve your equations from Steps 2 and 3 for the velocity of P. Do not forget that A will have both radial and transverse components of velocity.

## 5 thoughts on “Homework H5.M - Fa22”

1. skfree says:

Sometimes I get confused when working with polar coordinates. Does A have velocity in both the e_phi and the e_R directions? And does B only have velocity in the e_phi direction?

1. Aquinas says:

B is "rigidly attached" to the end of the bar so it only has velocity in the e_phi direction. Since A can slide on the bar it has velocity in both directions.

2. Joel Mason Laudo says:

Since Omega 1 isn't given a numerical value, should we leave it as a variable in our final answer?

1. Ethan Patrick Kovalan says:

Yeah, I think the only thing we can do is leave omega_1 as it is in our final answer.

3. Somya Jain says:

Are we meant to use the kinematics equations to find the angular velocity or is there another way or working that out?