7. A solid wheel with mass M, radius R, and rotational inertia MR²/2, rolls without sliding on a horizontal surface. A horizontal force F is applied to the axle and the center of mass has an acceleration a. The magnitudes of the applied force F and the frictional force f of the surface, respectively, are: (A) F = Ma, f = 0 (B) F = Ma, f = Ma/2 (C) F = 2Ma, f = Ma (D) F = 2Ma, f = Ma/2 (E) F = 3Ma/2, f = Ma/2

11. A small metal sphere is suspended from the conducting cover of a conducting metal ice bucket by a non-conducting thread. The sphere is given a negative charge before the cover is placed on the bucket. The bucket is tilted by means of a non-conducting material so that the charged sphere touches the inside of the bucket. Which statement is correct? (A) The negative charge remains on the metal sphere. (B) The negative charge spreads over the outside surface of the bucket and cover. (C) The negative charge spreads over the inside surface of the bucket and cover. (D) The negative charge spreads equally over the inside and outside surfaces of the bucket and cover. (E) The negative charge spreads equally over the sphere and the inside and outside surfaces of the bucket and cover.

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