Answer:
It took the projectile 120 s to reach the maximum height.
Explanation:
Given;
maximum height of the projectile, s = 180 km = 180,000 m
initial speed of the projectile, u = 3 km/s = 3000 m/s
final velocity at maximum height, v = 0
Apply the following kinematic equation for average velocity of the projectile;
[tex]s = (\frac{v+u}{2} )t\\\\(v+u)t = 2s\\\\t = \frac{2s}{v+u} \\\\t = \frac{2*180,000}{0+3,000}\\\\ t = 120 \ s[/tex]
Therefore, it took the projectile 120 s to reach the maximum height.
