Charlie wants to build a magnetic levitation train for his younger brother. Charlie has drawn a diagram of his train and has built the train. What should Charlie do next with his design? A. Test the device, get feedback from other people, and revise the design if needed.
B. Show his design to other people and get feedback before selling his design.
C. Publish his design in a magazine as is and wait for investors.
D. Test the device and sell it to the local veterinarian.

Aperson stands on a platform, initially at rest, that can rotate freely without friction. the moment of inertia of the person plus the platform is ip. the person holds a spinning bicycle wheel with its axis horizontal. the wheel has moment of inertia iw and angular velocity ωw. take the ωw direction counterclockwise when viewed from above. part a what will be the angular velocity ωp of the platform if the person moves the axis of the wheel so that it points vertically upward?