4 . 69 × 10 − 4 ± 0 . 27 × 10 − 4 kg m 2 for I , about 3.3% deviation from the theoretical value. If the upper and lower limits are considered, the moment of inertia is about ± 9% deviation from the theoretical value. The moment of inertia from the work–energy theorem yields greater deviation as compared to that obtaining from the Newton-based experiment. This discrepancy might result from the tennis ball which is designed to have a certain drag as it moves through air adding another source of resistance to the system. It is also worth noting that since the duration of each experiment is rather short, ∼ 1 . 6 s, the angular speed is still relatively small. Torque due to rotational friction can thus be omitted.