Question

A 10kg ball is dropped from a height of 10m.find the speed just before it reaches the ground

Answer 1

To Find :

• speed of ball just before it reaches the ground

Solution :

• mass of ball = 10kg
• height = 10m
• Acceleration due to gravity = 10m/s²

potential energy = mgh

= 10 × 10 × 10

= 1000 J

Kinetic energy = 1/2mv²

As we know that,

Initial potential energy = final kinetic energy

So,

⠀⠀⠀⠀⠀⇛ 1/2 × 10 × v² = 1000

⠀⠀⠀⠀⠀⇛ 5v² = 1000

⠀⠀⠀⠀⠀⇛ v² = 1000/5

⠀⠀⠀⠀⠀⇛ v² = 200

⠀⠀⠀⠀⠀⇛ v = √200

⠀⠀⠀⠀⠀⇛ v = 14.14

Hence

• Speed of ball just before it reaches the ground is 14.14m/s

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Answer 2

Given :-

• A 10kg ball is dropped from a height of 10m.

To find :-

• Find the speed just before it reaches the ground.

Solution :-

• Mass of ball = 10kg

• Height = 10m.

• Acceleration due to gravity = 10m/s².

Potential energy = mgh

= 10 × 10 × 10

= 1000 J

Kinetic energy = 1/2mv²

As we know,

• Initial potential energy = final kinetic energy

So,

• 1/2 × 10 × v² = 1000

• 5v² = 1000

• v² = 1000/5

• v² = 200

• v = √200

• v = 14.14

$\therefore$ Speed of ball just before it reaches the ground is 14.14m/s