The correct equation to use to calculate the kinetic energy of an object is:
[tex] K=\frac{1}{2}mv^2 [/tex]
where
m is the mass of the object
v is its speed
In this problem, the mass of the skydiver is [tex] m=72.0 kg [/tex], while its speed is [tex] v=79.0 m/s [/tex], therefore his kinetic energy is
[tex] K=\frac{1}{2}(72.0 kg)(79.0 m/s)^2=2.25 \cdot 10^5 J [/tex]
