A gun is positioned in a cliff 80m above sea level. It fires a shell, which leaves the muzzle with a velocity of 400 m/s in the horizontal direction. What is the closest distance that a ship can approach the cliff without being hit by the shell?
Y = 0.5gt^2 = 80m.
0.5 * 9.8t^2 = 80,
4.9t^2 = 80,
t^2 = 80 / 4.9 = 16.3,
t=sqrt(16.3) = 4.04s. = Time in flight.
X=Vi*t + 0.5gt. g = 0 for hor. motion.
X = 400*4.04 + 0.5*0*(4.04)^2,
X = 1616 + 0 = 1616m. An approaching ship would have to remain a distance >
1616m.