Astudent throws a set of keys vertically upward to his fraternity brother, who is in a window 3.95 m above. the brother's outstretched hand catches the keys 1.75 s later. (take upward as the positive direction. indicate the direction with the sign of your answer.) (a) with what initial velocity were the keys thrown?

More solar radiation is absorbed by earth’s surface than by

Consider a uniformly charged ring in the xy plane, centered at the origin. the ring has radius a and positive charge qdistributed evenly along its circumference. a)what is the direction of the electric field at any point on the z axis? . b)what is the magnitude of the electric field along the positive z axis? use k in your answer, where k=14πϵ0. d)the ball will oscillate along the z axis between z=d and z=−d in simple harmonic motion. what will be the angular frequency ω of these oscillations? use the approximation d≪a to simplify your calculation; that is, assume that d2+a2≈a2. express your answer in terms of given charges, dimensions, and constants

What is a costume plot? why is it important to a film or theater production?