EXPERIMENT 11. ROTATIONAL DYNAMICS 3. Moment of inertia. The moment of inertia can be calculated from I = τ α with uncer-tainty δI = I r ± δτ a τ a ² 2 + ( δα α ) 2 . Compute your experimental value for the inertia of the disk from the applied torque found in step 2 and the acceleration found in step 9 of the procedure and compare it to the calculated value found by summing that of the pulley (disk) and the bar: I disk = 1 2 m d r 2 d and I bar = 1 12 m b ( L 2 + w 2 ) 2 . Do these values agree within the experimental uncertainty? 4. Finally, check the work-energy relation, which state the total work done on a system equals the change in kinetic energy. There are two forces (gravity and friction) that do work on the system as the disk is spinning up: W g = mgh where h = Δ θr is the height the load mass fell while the spool was unwinding, and W f =-τ f Δ θ , where τ f = | I Δ α/ 2 | . The change in kinetic energy also has two terms (one for the rotation
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