4) A box of mass m is pressed against (but is not attached to) an ideal horizontal spring of force constant k and negligible mass, compressing the sp g the spring a distance x. After it is released, the box slides on a frictionless horizontal surface. If we repeat this experiment but instead compressing the spring a distance of 2x... (a) just as it moves free of the spring, the box will be traveling twice as fast as before. (b) just as it moves free of the spring, the box will be traveling four times as fast as before. (c) just as it moves free of the spring, the box will be traveling half as fast as before. (d) just as it moves free of the spring, the box will be traveling as fast as before. concepts. Choose the right answer and explain why. Show ALL your work. Hint: Use energy 5) As you are leaving a building, the door opens outward. If the hinges on the door are on your right, what is the direction of the angular velocity of the door as you open it? Choose the right answer and explain why. Hint: Use your right hand. (a) Up. (b) Down. (c) To your left. (d) To your right. (e) Into the paper. (d) Out of the paper. 6) (Optional for extra credit). Your physics professor showed you a demonstration about conservation of angular momentum using a rotating stool the last day of classes: she first started rotating with her arms outstretched and then she brought them inward to her stomach. (a) What happened with her angular velocity after bringing her arms inward her stomach with respect to her angular velocity when her arms were outstretched: was it larger, smaller or the same? Circle the right answer. (b) What physical quantity related with her mass did it change when she moved her arms towards her stomach? Consider your professor as a rigid body