The formula for kinetic energy is, [tex]{ E }_{ k }=\frac { 1 }{ 2 } \cdot m\cdot { v }^{ 2 }[/tex]
where m is mass and v is velocity.
Let's plug the given values in the formula.
[tex]{ E }_{ k }=\frac { 1 }{ 2 } \cdot m\cdot { v }^{ 2 }\\ \\ { E }_{ k }=\frac { 1 }{ 2 } \cdot 8\cdot { 4 }^{ 2 }\\ \\ { E }_{ k }=\frac { 1 }{ 2 } \cdot 8\cdot 16\\ \\ { E }_{ k }=4\cdot 16\\ \\ { E }_{ k }=64\quad \\ \\ [/tex]
It's kinetic energy is 64 Joules.