# Homework H5.L - Fa22

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 four-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?

## 7 thoughts on “Homework H5.L - Fa22”

1. skfree says:

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.

1. Enrico Setiawan says:

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

2. Saahas Kotian says:

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

1. JD says:

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

3. Aquinas says:

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.

4. Christian Charlson says:

Are the solution videos released? I cannot see them

1. Ethan Patrick Kovalan says:

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