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i can’t solve this question. i think this is the tougest proble so please help to solve this question.

i can’t solve this question. i think this is the tougest proble so please help to solve this question.

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Grade:12th pass

1 Answers

Arun
25750 Points
5 years ago
First, we write all the known quantities 
a= -10m's^2
s= 390 m
u= +10m/s
s=ut + 1/2at^2
s=10t + 5t^2
-390=10t + 5t^2
-78= 2t - t^2
t^2 - 2t - 78 = 0
d= b^2 - 4ac
d= 4 + 312
d= 316
-b±√d/2a
2±2√79/2=1±79.
therefore time taken to hit the ground will be 1+√79

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