Question

A ball when dropped from thetop of the building it takes 4 s to reach the ground find the height of the building (value of acceleration due to gravity 10ms^-2)
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CLASS 9 CH 8 PHYSICS ​

Answer 1

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Hope this helps ............

Answer 2

Answer:

• The height (H) of the Building is 80 meters.

Given:

1. Time taken (t) = 4 Sec.
2. Acceleration due to gravity (g) = 10 m/s²

Explanation:

$\rule{300}{1.5}$

As the question states that, Body is dropped from the top

Therefore, Initial velocity (u) will be Zero.

From Second Kinematic Equation we Know,

⇒ S = u t + 1 / 2 a t²

Where,

• S Denotes Distance.
• u Denotes Initial velocity.
• a Denotes acceleration
• t Denotes time taken.

Now,

⇒ S = u t + 1 / 2 a t²

Substituting the values,

⇒ H = u t + 1 / 2 g t²

∵ [ S = H ; a = g ]

⇒ H = 0 × 4 + 1 / 2 × 10 × (4)²

⇒ H = 0 + 1 / 2 × 10 × 16

⇒ H = 1 / 2 × 10 × 16

⇒ H = 10 × 8

⇒ H = 80

⇒ H = 80 m.

∴ The height (H) of the Building is 80 meters.

$\rule{300}{1.5}$