Question

A man falls 10 kg of stones on top of a 5 meter staircase when the stone reaches the ground, then what will be kinetic energy and its velocity​

Answer 1

Kinetic energy=1/2mv^2

where ,v=√2gh=√2×10×5=10m/s

therefore,

$kinetic \: energy = \frac{1}{2} \times 10 \times 100 = 500joule$

Answer 2

According to Law of Conservation of Energy during free fall ,

Kinetic energy of the stone when the stone reaches the ground = Potential energy of the stone when it was dropped by the man .

Potential energy = mass of the stone × acceleration due to gravity × height from which the stone was dropped .

Given :

Mass of the stone = 10 kg .

Height from which it was dropped = 5 m .

Acceleration due to gravity = 10 m/s² .

Kinetic energy = 10 kg × 5 m × 10 m/s²

⇒ Kinetic energy = 500 kg m/s²

⇒ Kinetic energy = 500 J

The kinetic energy of the body is 500 J .

We know that the initial velocity of the body ( u ) = 0 m/s .

Acceleration due to gravity ( g ) = 10 m/s² .

Height of the body ( h ) = 5 m .

By Laws of Motion we know that :

v² = u² + 2 g h

⇒ v² = 0 + 2 g h

⇒ v² = 2 g h

⇒ v² = 2 × 5 m × 10 m²/s²

⇒ v² = 100 m²/s²

⇒ v = √(100 m²/s² )

⇒ v = 10 m/s

The velocity of the body when it reaches the ground is 10 m/s .