Respuesta :

AL2006

Kinetic energy = (1/2) (mass) (speed)²

The rock's kinetic energy is not 

                           (1/2) (4 kg) (10 m/s)²

                      =   (1/2) (4 kg) (100 m²/s²)

                      =         200 Joules .

It may be more, or it may be less.  The only thing
we can be sure of is that it is not 200 Joules.

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