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Question
A body projected vertically up with a velocity of 10 m/s reaches a height of 20 m. If it is projected with a velocity of 20 m/s, then the maximum height reached by the body is:
Options
20 m
10 m
80 m
40 m
Solution
80 m
Explanation:
Initial velocity = u = 10 m/s
Height = Distance = S = 20 m
At highest point, Final velocity = v = 0
Acceleration = (a) = ?
Case − I
v2 − u2 = 2aS
(0)2 − (10)2 = 2a (20)
a = `-100/40` = −2.5 ms−2
Case – II
u = 20 m/s; v = 0
a = −2.5 ms−2; S = h /
v2 − u2 = 2aS
(0)2 − (20)2 = 2(−2.5)h
h = `400/5` = 80 m
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