Question

A ball of mass 50 kg falls from rest vertically down words through distance of 40 m and the ground, the
kinetic energy of the ball before it hits the ground is =
- * 9.8 J.​

Answer 1

The kinetic energy of the ball before it hits the ground = 2000 × 9.8 J

h = height of fall of the ball = 40 m

m = mass of the ball = 50 Kg

Let v be the velocity of the ball before it hits the ground .

v² = u² + 2gh

u = 0 , initially ball will be at rest .

=> v² = 0 + 2 × 9.8 × 40

=> v² = 784

=> v = 28 m/s

Velocity of the ball = 28 m/s

Kinetic Energy of the ball before it hits the ground = 1/2 mv²

=> 1/2 × 50 × 784

=> 19600 J

=> 2000 × 9.8 J

Kinetic Energy = 2000 × 9.8 J