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A ball is dropped from a bridge of 122.5 metres above a river . After the ball has been falling for two seconds, a second ball is thrown straight down after it. Initial velocity of second ball so that both hit the water at the same time is

A ball is dropped from a bridge of 122.5 metres above a river . After the ball has been falling for two seconds, a second ball is  thrown straight down after it. Initial velocity of second ball so that both hit the water at the same time is

Grade:11

3 Answers

Hasan Naqvi
97 Points
8 years ago
time taken by first ball to hit water can be found as
 
s= ut + ½ gt2
122.5 = ½ * 9.8 * t2
t2=  25
t =5 
 
Now the next ball must cover this distance in 3 s to hit water at same time.
122.5 = 3 u + ½ * 9.8 * 32
122.5 = 3u + 44.1
3u = 78.4
u= 26.133 m/s
 
Adarsh Anand
36 Points
7 years ago
 
time taken by first ball to hit water can be found as
 
s= ut + ½ gt2
122.5 = ½ * 9.8 * t2
t2=  25
t =5 
 
Now the next ball must cover this distance in 3 s to hit water at same time.
122.5 = 3 u + ½ * 9.8 * 32
122.5 = 3u + 44.1
3u = 78.4
u= 26.133 m/s
Kushagra Madhukar
askIITians Faculty 628 Points
3 years ago
Dear student,
Please find the solution to your problem.
 
Time taken by first ball to hit water can be found as
s= ut + ½ gt2
122.5 = ½ * 9.8 * t2
t2=  25
t =5
 
Now the next ball must cover this distance in 3 s to hit water at same time.
122.5 = 3 u + ½ * 9.8 * 32
122.5 = 3u + 44.1
3u = 78.4
u= 26.133 m/s
 
Thanks and regards,
Kushagra

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