physics
posted by Anonymous .
A plane is flying horizontally at a height of 500 m and a constant speed of 429 km/h when an object is projected vertically downward at an initial speed of 35.0 m/s. If air resistance is neglected, the average vertical component of velocity between the object's release and its striking the ground is

falls from 500 m with inital Vi = 35
v = Vi + a t so linear in time, average is half of (start + stop)
start v = 35
kinetic energy at ground = (1/2) m (35^2) + m g (500) = (1/2) m v^2
so
v^2 = 9.81 * 1000 + 1225
v = 105 m/s at ground
average v = (35 + 105)/2 = 70 m/s