Physics Challenge , Dare to Solve Question number , 28
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let t is the time of free fall of body
velocity of striking time=-gt
velocity of body just 1second before=-g (t-1)
now use v^2=u^2+2as
s=1/2g (1-2t)
now displacement of body first 3second=0-1/2g (3)^2=-45m
a/c question
-45=1/2g (1-2t)
t=5 second
hence time of free fall =5 sec
velocity of striking time=-gt
velocity of body just 1second before=-g (t-1)
now use v^2=u^2+2as
s=1/2g (1-2t)
now displacement of body first 3second=0-1/2g (3)^2=-45m
a/c question
-45=1/2g (1-2t)
t=5 second
hence time of free fall =5 sec
Answered by
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5 sec is the answer,
first we need to find the displacement for first three second displacement,
= 1/2gt² = 4.905(3)² = 44.145 m Free-Fall displacement during last second = 44.145 m
First three second displacement = 1/2gt² = 4.905(3)² = 44.145 m
Free-Fall displacement during last second = 44.145 m
V average during last second of Free-Fall = 44.145/1 = 44.145 m/s
Vaverage = (Vo+Vf)/2 = 44.145
Vo+Vf = 88.29
Vo = gt {where t = Free-Fall time - 1
Vf = 88.29 - 9.81t
Vf = g(t+1) = 9.81t + 9.81
88.29 - 9.81t = 9.81t + 9.81
88.29 - 9.81 = 19.62t
19.62t = 78.48
t = 4 s
time to Free-Fall = t + 1 = 5 s ANS
first we need to find the displacement for first three second displacement,
= 1/2gt² = 4.905(3)² = 44.145 m Free-Fall displacement during last second = 44.145 m
First three second displacement = 1/2gt² = 4.905(3)² = 44.145 m
Free-Fall displacement during last second = 44.145 m
V average during last second of Free-Fall = 44.145/1 = 44.145 m/s
Vaverage = (Vo+Vf)/2 = 44.145
Vo+Vf = 88.29
Vo = gt {where t = Free-Fall time - 1
Vf = 88.29 - 9.81t
Vf = g(t+1) = 9.81t + 9.81
88.29 - 9.81t = 9.81t + 9.81
88.29 - 9.81 = 19.62t
19.62t = 78.48
t = 4 s
time to Free-Fall = t + 1 = 5 s ANS
aqibshaikh:
Hope its useful to you. all the best
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