Question

a child drops of ball from a height of 20m. assume that its velocity increase uniformly at a rate of 10m/s². Find:-
i) velocity with which the ball strike the ground
ii) the time taken by the ball to hit the ground.
I will report in correct answers! ​

Answer 1

Answer

• Velocity with which the ball strike the ground is 20 m/s
• The time taken by the ball to hit the ground is 2 s

Given

• A child drops of ball from a height of 20 m. assume that its velocity increase uniformly at a rate of 10 m/s²

To Find

i )   velocity with which the ball strike the ground

ii )  The time taken by the ball to hit the ground

Concept Used

Equations of motion

• v² - u² = 2as
• v = u + at

Solution

Initial velocity , u = 0 m/s [ ∵ Drops from height ]

Height , s = 20 m

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

Final velocity , v = ? m/s

Time , t = ? s

Apply 3 rd equation of motion .

⇒ v² - u² = 2as

⇒ v² - 0² = 2(10)(20)

⇒ v² = 400

⇒ v = 20 m/s

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Final velocity , v = 20 m/s

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Apply 1 st equation of motion .

⇒ v = u + at

⇒ 20 = 0 + (10)t

⇒ 20 = 10t

⇒ 10t = 20

⇒ t = 2 s

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Time , t = 2 s

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