When an object is dropped from the top of a tall cliff, your teacher tells you to use -10 m/s2 for the approximate acceleration due to gravity. what sign should the displacement of the object have and why? a) the displacement should be positive, because it only moves in one direction. b) the displacement should be positive, because this choice would make calculations easier c) the displacement should be negative, because the negative represent a downward direction. d) the displacement should be positive, because you can never have less than zero displacement. the truck is described as travelling at 30mph to the west. the quantity described here is a(n) a) speed b) velocity c) acceleration d) kinetic energy