Question

PHYSICS
A ball is thrown vertically upwards with a velocity of 20ms
−1
from the top of a multi storey building.The height of the point where the ball is thrown 25 m from the ground.How long will it be before the ball hits the ground ? Take g=10ms
−2
.
December 20, 2019avatar
Lakshya Mathew
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ANSWER
Time to reach maximum height can be obtained from v=u+at
0=20+(−10)t
t=2s
s=ut+0.5at
2
=20(2)+0.5(−10)(2)
2
=20m
Thus, total distance for maximum height is 45 m
s=ut+0.5at
2

45=0+0.5(10)(t
′
)
2

t
′
=3s
Total time= 3+2= 5s
​

Answer 1

Answer:

yes it is right.. .. . but here t=12s not 5s

45=0+0.5(10)t

45/5=t

9=t

3+9=12s