Question

7. A stone is dropped in to water from a tree 78.4m above water. One second later, another stone thrown
Vertically downward. Both stones strike water simultaneously. What is the initial speed of second stone?​

Answer 1

Answer:

11.82 m/s

Explanation:

t = √2h/g = √78.4/5 = √15.68 = 3.96 s

v = u + gt = u + 2.96x10 = u + 29.6

H = ut + gt²/2

ut + gt²/2 = H

2.96u + 5(2.96²) = 78.4

2.96u = 78.4 - 43.81 = 34.99

u = 34.99/2.96 = 11.82 m/s