Question

A coconut is hanging on a tree at a height of 15 m from the ground. A body launches a projectile vertically upwards with a velocity of 20 m/s. After what time will the projectile pass by the coconut. Explain the two answers you get in this problem.

Answer 1

distance of coconut from the ground$s=15m$

$u=20\frac{m}{s}$

$a=9.8\frac{m}{s^2}$

from

$s=ut+\frac{1}{2}a{t}^2$

$15=20t-\frac{1}{2}10t^2$

$3=4t-t^2⟹t^2-4t+3=0⟹(t-1)(t-3)=0⟹t=1,3$

at time t=1 second projectile passes the coconut by going upwards and t=3 seonds it passes the coconut coming downwards