1) A ball is thrown from a tall building at some angle with respect to the horizontal. By measuring the height of the building and the distance that the ball lands from the base of the buiding, one can uniquely determine the speed of the ball when it hits the ground. I put this down as false because wouldn't you need to know the angle? 2) The gravitational force between the Earth and the Moon results in work being done on the Moon. False. 3) If only conservative forces act on an object, a decrease in the object's potential energy will always correspond to a decrease in its kinetic energy. I'm confused at what this is asking, but I put this down as false. 4) Gravity is a conservative force. True. 5) If a rock, initially at rest, is dropped from a tall building, the speed of the rock when it hits the ground will only depend on its initial height above the ground. True 6) The total mechanical energy of a box sliding across a rough surface is conserved. True.