A horizontal spring with spring constant {eq}100\ N/m {/eq} is compressed {eq}20\ cm {/eq} and used to launch a {eq}2.5\ kg {/eq} box across a frictionless, horizontal surface. After the box travels some distance, the surface becomes rough. The coefficient of kinetic friction of the box on the surface is {eq}0.15 {/eq}.

A. What is the speed of the box immediately after it loses contact with the spring?

B. Find the change in kinetic energy of the box when it comes to a stop.

C. Draw the free body diagram of the block when it is on the rough surface.

D. Use work and energy to find how far the box slides across the rough surface before stopping.

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