Adding a child at the rim of a merry-go-round changes the angular acceleration because it changes the:

1. The applied torque can be kept the same in both cases. 2. To solve for the angular acceleration, you first calculate the torque, which is the same in both cases. 3. You then calculate the moment of inertia, which is greater in the second case. 4. A larger moment of inertia with the same torque gives a smaller angular acceleration. 5. The child contributes as a point mass at a distance of 1.25 metres from the axis. _Source: OpenStax College Physics for AP(R) Courses 2e (CC BY 4.0), Ch 10 'Rotational Motion and Angular Momentum', sections 10.1-10.7_