A boy tries to hit a bird by throwing stone vertically upward but the stone misses the bird. The stone goes upward in the air for 3s. While returning after 1s the stone hits the bird.

1. Find the maximum height reached by the stone.
2. At what height was the bird hit?
3. What value is not shown by the boy?

From first equation of motion:

v = u-gt     v=0 at topmost point taking g=10 m/s²

u = gt 
  = 3*10 = 30 m/s

now, from third equation of motion:

v² = u² -2gh

2*10*h=30²

h = 45 m        (ANS (i))

now, while returning u = 0 m/s and g = 10m/s²

applying second equation of motion height fell can be calculated as under:

h = ut + 1/2 gt²
h = 0*t + 1/2 *10*1

height fell = 5m    (ANS (ii))

(iii) The boy has not shown the angle at which he threw the stone.