Question

3. From the top of a multi-storeyed building, 39.2 m
tall, a boy projects a stone vertically upwards with
an initial velocity of 9.8 ms such that it finally
drops to the ground. (i) When will the stone reach
the ground ? (ii) When will it pass through the point
of projection ? (iii) What will be its velocity before
striking the ground ? Take g = 9.8 ms ?
(Ans. 4s, 2s, 29.4 ms -1)
plz answer jaldi dedo​

Answer 1

Answer:

I) s = it+1/2×at

-39.4 = 9.8×t+1/2×9.8×t²

-8 = 2t-t²

t²-2t-8 = 0

t=4 second

II)V= u+at

0 = 9.8-(9.8)t

t =1

T = 2t

.'. 2 seconds

III)V² = ú²+2as

= (9.8)²+2(09.8)39.2

= 29.4m/s