http://www.forrestrace.com/rock-grinding-3/
In how many seconds after being thrown does the rock strike the ground?
A rock is thrown vertically upward with a speed of 13.0 m/s from the roof of a building that is 50.0m above the ground. Assume free fall.
In how many seconds after being thrown does the rock strike the ground?
☻equation of motion of the rock is y(t) =v*t –0.5g*t^2;
☺now y=-50 m; thus –50 = 13*t –0.5g*t^2; brushing we get
g*t^2 -26t –100=0, hence t=(13 +√(169+100g))/g = 4.79s;
C-Rock: “Grinding On Feat. Trae, Smoke, Nygel