Question

(3) 4th and 6" se
4. A ball is dropped from a bridge of 122.5 metre
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
(1) 49 m/s
(2) 55.5 m/s
(3) 26.1 m/s
(4) 9.8 m/s
in the solution of this question why the height of first ball is taken as 1/2 gt2 and not ut-1/2gt2
explain ​

Answer 1

Answer:

S=UT +1/2at square

S=0+1/2*9,8 t square

122. 5 =4.9t square

25= t square

T= 5 sec

Second ball has 2 second less to fall

So t=3

S=UT +1/2 at square

122. 5=3u+44.1

=78.4/3

=26.1

It is because u is o