A plastic ball in a liquid is acted upon by its weight and by a buoyant force. The weight of the ball is 2.6 N. The buoyant force has a magnitude of 4.4 N and acts vertically upward. At a given instant, the ball has zero velocity. At that instant, an external force acting on the ball imparts an acceleration of 3.0 m/s2 in the downward direction of the ball. The external force, including direction, is closest to:

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.