[b]An object is launched at 29.4 meters per second (m/s) from a 78.4-meter tall platform. The[br]equation for the object's height [i]s[/i] at time [i]t[/i] seconds after launch is[/b] [math]s\left(t\right)=-4.9t^2+29.4t+78.4[/math], [br][b]where [/b][b][i]s[/i][/b][b] is in meters. When does the object strike the ground?[/b][br][br][br]