Question

a stone is thrown upward with an initial velocity 30 m/s the same instant another stone is dropped from the tower of height 40m . when and where these two stones cross eachother​

Answer 1

a=-g=-9.8
u=30m/s
t=?
t=t1+t2
v=0,x=h1

$v {2} = u {2} + 2as$
0=30×30+2×(-9.8)h1
19.6h1=900
h1=900÷19.6
h1=45.91
X=h1+h2
=45.91+40
=85.91
a=v-u÷t
time taken from A to B
t1=v-u÷a
=0-30÷9.8
=3.061sec
time taken from B to C
x=ut2+1/2(at^2)
85.91=30×t2+1/2×9.8×t2^2
t2^2=85.91÷4.9
t2=1 .891sec
t=t1+t2
t=3.061+1.891
t=4.952 sec