Homework H5.G - Fa22

Problem statement
Solution video


Any questions??

Four-step plan

Step 1: FBD
Draw a free-body diagram for the disk.

Step 2: Kinetics - Work/energy
Write down the kinetic energy and potential energy expressions for the disk, along with the work done on the disk by non-conservative forces. Note that point C is the instant center (zero velocity point) for the disk. Because of this, you are able to write down the KE for the disk as Tdisk = 0.5*ICω2, if you choose to do so. The work done by F is equal to U = FsA, where sA is the distance traveled by end A of the cable.

Step 3: Kinematics
Here you need to relate the distance traveled by point O to the distance traveled by end A of the cable (these are not the same). In doing this, recall that C is the instant center of the disk as it rolls without slipping.

Step 4: Solve
Solve your equations from Steps 2 and 3 for the speed of point O.


11 thoughts on “Homework H5.G - Fa22”

    1. Assuming you mean relating it for velocity, you can use C as the Instant Center and measure both the velocity of O, and then the point directly above O, which will be equal to the velocity of A.

        1. Once you find the relationship between the velocity of O and the velocity of A, you can integrate that equation to find the change in the distance traveled. For example, if v_B = 2*v_A, then delta_s_B = 2*delta_s_A

  1. Do we start by finding the distance of point A to the center O or should we use C as instant center to find the distance and use that to find the velocity of A?

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