You drop a ball from a window on an upper floor of a building and it is caught by a friend on the ground when the ball is moving with speed vf. you now repeat the drop, but you have a friend on the street below throw another ball upward at speed vf exactly at the same time you drop your ball from the window. the two balls are initially separated by 28.7 m. (a) at what time do they pass each other? (b) at what location do they pass each other relative the window?

One kind of e-book display consists of millions of very small spheres that float in a thin fluid layer between two conducting transparent plates. each sphere is black on one side and white on the other, and possesses an electric dipole moment directed from the white side to the black. when an electric field is applied between the plates, the spheres rotate so that their dipole moment lines up with the field. depending on the fields direction, either the black or the white sides of th espheres can be made visible.the dipole moment of the spheres can be modeled as two opposite charges of magnitude 3.5 x 10^-15 c, separated by a distancce of 100 micrometers (um). what is the maximum possible torque on a sphere if the electric field between the transparent plates is 4.0 x 10^5 n/c