A boy tries to hit a bird by throwing a stone vertically upward but the stone misses the bird. The stone goes upwards in the air for 3 s. While returning after 1 second the stone hits the bird. Answer the following questions based on the information given: (𝒊) Find the maximum height reached by the stone. (𝒊𝒊) At what height was the bird hit? (𝒊𝒊𝒊) What value is not shown by the boy?

(𝐢) Time of ascent = 3s

Initial velocity = u

Final velocity, v = 0 m/s

Acceleration, a = g = – 9.8 m/s²

∴                      v = u+ at

⟹                   0 = u + (- 9.8) x 3

⟹                   0 = u – 29.4

∴                     u = 29.4 m/s

∴ Maximum height of the stone reached = {v^2 - u^2 \over 2a}           [∵ 𝑣 ² – 𝑢 ² = 2as]

= {(0)^2− (29.4)^2 \over 2 \times (−9.8)} = {−864.4 \over -19.6} = 44.1 m

(ii) The bird was hit after a second while returning.

∴ Initial velocity, u = 0 m/s

Distance travelled = s

Time taken = 1 s

Acceleration, a = g = 9.8 m/s²

s = 𝑢𝑡 + {1\over2} gt²

= 0 x 1 + {1\over2} x 9.8 x (1)² m = 0 + ({1\over2} x 9.8) = 4.9 m

The height of the bird from the ground = 44.1 m – 4.9 m = 39.2 m

(𝐢𝐢𝐢) Each and every living organism is a part and parcel of our life, because living organisms maintain biodiversity on earth. Therefore, we should treat the living beings in a polite way. This value is not shown by the boy as he hits the bird.