Gravitation

Que 1. 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?

Ans. (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 =                   

                                                                         =   

(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
                                                                        
                                                                     

             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.