Physics, asked by soni2003, 9 months ago

please solve this question​

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Answered by khushal546
0

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

-u²=2as

0²-=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= \frac{u}{2}

from equation of motion

v=u+at

\frac{u}{2}=u+at

u=2(u+at)

-30=2(-30+10t)

-30=-60+20t

-30+60=20t

30=20t

t=\frac{30}{20}

t=1.5sec

additional information;

distance at which velocity become half is given by

from equation of motion

-u²=2ax

 \frac{u}{2}²-u²=2*10*x

\frac{u²}{4}-u²=20x

\frac{u²-4u²}{4}=20x

-4u²=4*20x

-3u²=80x

-3*(-30²)=80x

-3*900=80x

-2700=80x

x=-33.7m (or) 33.7m

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