A small airplane flying horizontally with a speed of 180 mph at an altitude of 4
ID: 2277095 • Letter: A
Question
A small airplane flying horizontally with a speed of 180 mph at an altitude of 400 ft above a remote valley drops an emergency medical package at A. The package has a parachute which deploys at B and allows the package to descend vertically at a constant rate of 6 ft/s. If the drop is designed so that the package is to reach the ground 37 seconds after release at A, determine the horizontal lead L so that the package hits the target. Neglect air resistance.
Explanation / Answer
let time taken to reach B is t.
1 mile/hr=1.467 ft/sec
so 180 mph=264 ft/sec
so 264*t=L....(1)
in t seconds,height descended=0.5*32*t^2=16*t^2
after that it takes 37-t seconds to reach the ground.
then height of B=6*(37-t)
so 16*t^2+6*(37-t)=400
solving for t,we get
t=3.528 sec
so L=264*t=931.4 ft