Question on kinetic energy?

Question

If two 10 kg cannon balls, each travelling at 200 m/s, collide head-on what is the total kinetic energy of the collision? If just one cannon ball, travelling at twice the speed, hits a solid stationary wall then what is the kinetic energy of the collision?

Answer 1

The total kinetic energy of the impact is:

K (total) = ½mv² + ½mv²

= (0.5 x 10 kg x (200 m/s)²) + (0.5 x 10 kg x (200 m/s)²)

= 200,000 J + 200,000 J

= 400,000 J

The kinetic energy of the cannon ball with twice the speed is:

K = ½mv²

= 0.5 x 10 kg x (400 m/s)²

= 800,000 J