**1. The problem statement, all variables and given/known data**

An army tank on a mountainside fires its gun horizontally. The shell strikes the ground at a horizontal distance of 6000 m away from the tank. As the vertical component of the shell’s striking velocity is vy=200 m/s, how soon after it is fired does the shell strike the ground? (g=10 m/s2)

**2. Relevant equations**

v^2=2ax (1)

x=at^2/2 (2)

**3. The attempt at a solution**

40000=2*a*6000

then find t with (2) but why is it the component vy?

http://ift.tt/TdO6mM