Physics C mech 2004 FR (2) - Pulley and Rotational Inertia

[joej24]

Homework Statement

http://apcentral.collegeboard.com/apc/public/repository/ap04_frq_physics_cm_36191.pdf
The problem can be found here. I am stuck on problem 2 d.

Homework Equations

I = m(g-a)R² / a //found in part c

The Attempt at a Solution

I don't understand why the Rotational Inertia would change. Can someone describe to me the change in the layout of the disk and pulley too?

 

[Quinzio]

One possible answer could be that the data interpolation led to a certain error in the estimation of inertia.

Other reasons I can't really imagine.

 

[joej24]

data interpolatin? What's that?

bump

 

[jhae2.718]

Because I'm lazy, I just looked up the scoring guidelines: http://apcentral.collegeboard.com/apc/public/repository/ap04_sg_physicsc_mech.pdf

The discrepancy comes from the effect of the string. (That "real world" stuff we tend to ignore to simplify things...)