Q. A 45.0 kg girl is standing on a 130 kg plank. The plank, originally at rest, is free to slide on a frozen lake, which is a flat, frictionless surface. The girl begins to walk along the plank at a constant velocity of 1.33 m/s relative to the plank.
Q. An air-filled parallel-plate capacitor has plate area A and plate separation d. The capacitor is connected to a battery that creates a constant voltage V. Find the energy U_0 stored in the capacitor.