Problem statementSolution video |

**DISCUSSION THREAD**

**Discussion and hints:**

Note that the animation above is for a generic set of parameter values that may or may not be the ones assigned for the problem this semester.

Recall the following *f**our-step plan* outline in the lecture book and discussed in lecture:

**Step 1: FBDs**

Draw a *single* free body diagram for the system made up of bar OA and particle P, *combined*.

**Step 2: Kinetics (impulse/momentum)**

- From you FBD above, what can you say about the moments acting about the fixed point O in your system? What consequence does this have on the angular momentum about point O for the system?
- Use the coefficient of restitution, COR, equation relating the "n-components" of velocity for P and end A of the bar. (You may want to review Section 4.C of the lecture book in regard to impacts and the COR.)

**Step 3: Kinematics**

Note that bar OA rotates about point O. What does that say about the direction of the velocity of point A on the bar after impact? Study the animation above. Do your kinematics agree with what you see about the direction of the velocity of A?

**Step 4: Solve**

Solve your equations above for the speed of slider B.

Any questions?

Do P and A have the same velocity in the n direction after the impact? If I plug that and the initial condition that the bar is stationary into the coefficient of restitution equation, I get 0 = -2v_2 / v_B1, making v_2 equal to 0, but I feel like that doesn't make sense.

You know P and A have the same velocity from the COR equation, so if you plug that result back into the equation you will of course get 0.

Once you know Vp2=Va2, move on to conservation of momentum equations

Does the second moment of inertia include the mass of the particle because e=0 so they stick together?

No, e=0 just means that they have the same velocity after impact so the second moment of inertia just includes the bar.

If e=0, I believe we don't need to deal with it for this problem since it won't affect the velocity after impact.

Are the solution videos released? I cannot see them

It hasn't been linked in the actual homework post, but there is a section in the header dedicated to the solution videos.