Question

a stone is dropped from the top of the top of cliff reaches it foot in 4 s. calculate the height of the cliff and the velocity with which stone reaches the ground.(g=10m\s^2)
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Answer 1

Answer:

h = 80 m,  v = 40 m/s

Explanation:

Given

a stone is dropped from the top of the cliff

Time taken for stone to reach the ground = 4s

Let height be 'h' and final velocity be 'v'

a = g = 10m/s²

As it is a freely falling body initial velocity is zero i.e., u = 0.

We know that

s = ut + 1/2 at²

⇒h = ut + 1/2 at²     [ here displacement of stone is height of the cliff]

⇒h = 0 + 1/2 10*(4)²

∴ h = 5*16 = 80 m

∴ h = 80 m

We know that

v = u + at

⇒v = 0 + 10*4

∴v = 40 m/s