Question

how long will a stone take to fall from the top of a building 80 metre high and what will be the velocity of the stone or reaching on the ground
$<marquee \: h$
$g \: = 10m \: per \: {s}^{2}$
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Answer 1

Given:

• Initial velocity, u = 0

• Acceleration due to gravity, g = 10 m/s²

• Height, h = 80 m

To be calculated:

Calculate the final velocity of stone?

Formula used:

v² = u² + 2gh

Solution:

We know that for a freely falling object:

v² = u² + 2gh

Putting the values in the above formula, we get

v² = ( 0 )² + 2 × 10 × 80

v² = 20 × 80

v² = 1600

v = √1600

v = 40 m/s

Thus, the velocity of stone reaching on the ground will be 40 metres per second.