Ball #A# is dropped from rest from a building of height #H# exactly when ball #B# is thrown up vertically. When they collide #A# has double the speed of #B#. If the collision occurs at height #h# what is #h/H#?

Write equations for heights #y_A# and #y_B#, and velocities #v_A# and #v_B#. What can you say about these at the time of the collision?