Problem statementSolution video |

**DISCUSSION THREAD**

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**DISCUSSION**

**Four-step plan**

**Step 1: FBD**

Draw *individual* free-body diagrams for the collar A and the disk. Do not forget the friction force on the disk at C when drawing your FBD of the disk. Define a coordinate *x* that describes the motion of the disk center O. Let's say you choose *x* to be positive to the left. Be sure that the directions of the spring forces on the collar are consistent with your definition of *x*.

**Step 2: Kinetics - Newton/Euler**

Write down the Newton/Euler equations for the collar and the disk. Be sure to abide by the sign conventions defined for *θ* and *x *when writing down these equations.

* Step 3: Kinematics*The kinematics that you need here are to relate

*θ*and

*x*. Be reminded that the contact point C is the instant center for the disk. As before, be sure to abide by the sign conventions defined for

*θ*and

*x*. For x defined positive to the left and

*θ*defined positive

*CCW*, we have

*x*=

*+Rθ*

*.*

**Step 4: Equation of motion**

Combine your equations from Steps 2 and 3 to end up with the differential equation of motion for the system.