Question

A stone is dropped from a height of 29m.
(i) How long will it take to reach the ground?
(ii) What will be its speed when it hits the ground?​

Answer 1

Answer:

(i) 2.43 seconds.

(ii) 23.84 m/s.

Explanation:

Given that,

A stone is dropped from a height of 29 m, s = 29 m.

The stone is coming downward. So, acceleration due to gravity, g = 9.8 m/s².

And , Its Initial velocity is 0 m/s.

(i) Here, We have to find time taken by the stone to reach the ground.

We know,

• s = ut + 1/2 gt²

Put all values :

$\implies$ 29 = [(0) × t] + 1/2 × (9.8) × t²

$\implies$ 29 = 0 + 9.8/2 × t²

$\implies$ 29 = 4.9 × t²

$\implies$ 29/4.9 × t²

$\implies$ 5.92 = t²

$\implies$ t = √5.92

$\implies$ t = 2.43

Thus,

It will take 2.43 second to reach the ground.

(ii) We have to find the speed of stone when it hits the ground. Means final speed (v) of stone.

We know,

• v² - u² = 2gs

Put all values :

$\implies$ v² - (0)² = 2 × 9.8 × 29

$\implies$ v² - 0 = 568.4

$\implies$ v = √568.4

$\implies$ v = 23.84

Therefore,

Speed of the stone when it hits the ground is 23.84 m/s.