A mass of 8 kg. moves at a rate of 14.3m / sec. what is the KE developed by the mass

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

= (1/2) (8 kg) (14.3 m/s) ²

= (4 kg) (204.49 m²/s²)

= 817.96 joules.

The mass doesn't 'develop' that energy. That's the energy it has

when it's moving 14.3 m/s, and you have to give it that energy in

order to make it move at that speed. The energy has to come from

someplace, and if you can't deliver it to the mass, then there's no way

to make the mass move at 14.3 m/s.