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