An aeroplane drops a slack of rice as shown in the figure with a horizontal velocity of 100 km/s. If the altitude of its travel is 10,000 km, from the ground determine the time needed for the sack to strike the ground.

1) 47.50 s
2) 45.15 s
3) 56.75 s
4) 35.65 s

The origin of coordinates is established at point K, where the initial velocity has   (vK)x=100 km/s and (vK)y=0 as its components. Also between points K and Q the accleration is g = -9.8m/s2.
The vertical distance from K to Q can be equated to get the time required,
y = y0 + (vK)yt + 0.5(-g)t2
-10,000 = 0+0+0.5(-9.81m/s2)t2, t = 45.15 s

So, the time taken t = 45.15 s