Answer:
Maximum height: 20.4 m, height at 30 s: -274 m
Explanation:
If you want to find the height of the ball after 30 seconds, we must use the equation:
[tex]v=u+at[/tex]
where
u = 20 m/s is the initial velocity
a = g = -9.8 m/s^2 is the acceleration of gravity
t is the time
Substituting t = 30 s,
[tex]v=20+(-9.8)(30)=-274 m[/tex]
This means that the ball is 274 m below its original level.
If you want to find the maximum height, then it can be find by using the law of conservation of energy: in fact, at the maximum height, all the initial kinetic energy has been converted into potential energy, so
[tex]mgh = \frac{1}{2}mu^2[/tex]
And solving for h, we find the maximum height:
[tex]h=\frac{u^2}{2g}=\frac{20^2}{2(9.8)}=20.4 m[/tex]
