Sandy releases a javelin 1.6 m above the ground with an initial vertical velocity of 25 m/s. how long will it take the javelin to hit the ground?

Time taken for the javelin to hit the ground will be given by:
A(t)=V'(t)=S''(t)
A(t)=-9.8m/s
⇒V(t)=-9.8t/1+C m/s

Where C is the initial velocity:
⇒V(t)=-9.8t+25
⇒S(t)=-9.8t²/2+25t/1+C
⇒S(t)=-4.9t²+25t+C
but the C is the initial vertical displacement, hence:
S(t)=-4.9t²+25t+1.6m

The time taken to hit the ground will therefore be:
S(t)=0
-4.9t²+25t+1.6=0