Question

A stone dropped from the roof of a building takes 4s to reach the ground.
Calculate the height of the building.

Answer 1

Answer :

Time taken by stone to reach the ground = 4s

We have to find the height of the building$.$

⧪ For a body falling freely under the action of gravity g is taken positive.

In this case, constant acceleration due to gravity acts in downward direction throughout the motion.

First equation of kinematics :

• H = ut + 1/2 gt²

Initial velocity = zero

⭆ H = 1/2 × gt²

⭆ H = 1/2 × (10)(4)²

⭆ H = 1/2 × (160)

⭆ H = 80m

Cheers!

Answer 2

Given:-

• Time taken by stone to reach the ground =4s

To find :-

• The height of the building.

Solution:-

Here, g is taken positive as it is freely falling body.

Also, initial velocity is zero .

We know,

✧$\pink{H = ut + 1/2 gt²}$

Therefore,

➝H = 1/2 × gt²

➝H = 1/2 × (10)(4)²

➝ H = 1/2 × (160)

➝ $\underline{\boxed{\pink{H = 80m}}}$

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