Question

a ball is dropped from bridge 122.5 metres above a river.After the ball has been falling for 2 seconds,a second ball is thrown straight down after it. What must be its initial velocity so that both hit water at the same time?
Answer guyz....

Answer 1

The initial velocity of the ball should be 5 m/s.

Answer 2

Answer:

For the first ball: Let it takes ′t′sec  to river.

⇒122.5=21×g×t2------------------------(1)$

for second ball: time taken =t−2sec.

122.5=u(t−2)+21g(t−2)2--------------(2)

⇒2gt2=ut−2u+2gt2+2g−2gt

⇒(2g−u)t=2g−2u

⇒t=2g−u2g−2u

from(1)

t2=g2×122.5

t=982×122.5=735=5sec

⇒10g−5u=2g−2u

Explanation:

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