Kinematics Question 197

Question: A particle is dropped under gravity from rest from a height $ h(g=9.8m/{{\sec }^{2}}) $ and it travels a distance $ 9h/25 $ in the last second, the height $ h $ it’s [MNR 1987]

Options:

A) 100 m

B) 122.5 m

C) 145 m

D) 167.5 m

Show Answer

Answer:

Correct Answer: B

Solution:

Let h distance is covered in n sec
$ \Rightarrow h=\frac{1}{2}gn^{2} $ -(i) distance covered in $ n^{th} $ sec $ =\frac{1}{2}g(2n-1) $
$ \Rightarrow \frac{9h}{25}=\frac{g}{2}(2n-1) $ -(ii) From (i) and (ii), $ h=122.5\ m $



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