s (distance) = ?
v (final velocity) = 0 m/s
u (initial velocity) = −20 m/s
a (acceleration due to gravity i.e., g) = 9.8m/s2
υ2 − u2 = 2as
(0)2 − (−20)2 = 2 × 9.8 × S
−400 × 2 × 9.8 = S
S = −20.4 m
The negative sign comes because the displacement is upward and we have considered the motion along the acceleration due to gravity (downward) as positive. Thus, the required distance is 20.4 m.
Answer: s = 20.4 m