please solve this question
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your answer is 1.5 sec
given➡
total distance, s=45m
at max height velocity is zero, v=0
initial velocity, u=?
total time taken, T
acceleration due to gravity,g=10m/s
explanation➡
let A be the point where velocity of ball become half that of original velocity and t be time taken.
proff➡
from equation of motion
v²-u²=2as
0²-u²=2*10*45
-u²=900
-u=√900
-u=30m/s
.....(-ve sin show that u is constantly decreasing)
since at point A velocity become half, mean
v=
from equation of motion
v=u+at
=u+at
u=2(u+at)
-30=2(-30+10t)
-30=-60+20t
-30+60=20t
30=20t
t=
t=1.5sec
additional information;
distance at which velocity become half is given by
from equation of motion
v²-u²=2ax
²-u²=2*10*x
-u²=20x
=20x
u²-4u²=4*20x
-3u²=80x
-3*(-30²)=80x
-3*900=80x
-2700=80x
x=-33.7m (or) 33.7m
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