Question

A stone is dropped from the roof of a building . It takes 4 seconds to reach the ground . Find the height of the building . (Take g = 9.8 m/s^2)
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Answer 1

Given

• Time = 4 sec
• g = 9.8 m/s²

To Find

• Height of th building

Solution

☯ s = ut + ½at²

• Also known as the second equation of motion

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✭ According to the Question :

⇒ s = ut + ½at²

• s = ?
• u = 0 m/s (body starts from rest)
• t = 4 sec
• a = g = 9.8 m/s²

⇒ s = 0 × 4 + ½ × 9.8 × 4²

⇒ s = ½ × 9.8 × 16

⇒ s = 9.8 × 8

⇒ s = 78.4 m

∴ The height of the building is 78.4 m

Answer 2

QUESTION :-

A stone is dropped from the roof of a building . It takes 4 seconds to reach the ground . Find the height of the building . (Take g = 9.8 m/s^2)

GIVEN :-

4 seconds to reach the ground

TO FIND :-

Find the height of the building = ?

SOLUTION :-

Given, Initial velocity of object, u = 0

Acceleration due to gravity, g = 9.8m s ^ - 2

Time, t = 4 s

We know that,

h = ut + 1/2 gt²

Substituting the values, we get

h = 1/2 × 9.8 × 16 = 78.4m

Thus, the height of building is 78.4 m..