Speed in a specific direction

Velocity a vector quantity, is the speed that has a specific direction.

Examples:
8 m/s to the East
20000 km/h Northwest

My car is running at a speed of 40 mi/h going North to my school.

In the question it is already given that the football player is 80 kg.
Then the mass of the football player = 80 kg
Velocity at which the football player is running = 8 m/s
Kinetic Energy = 0.5 • mass • square of velocity
Now we have to put the known data in this equation to find the actual velocity of the footballer.
 So
Kinetic Energy of the footballer = 0.5 * 80 * (8 * 8) 
                                                 = 0.5 * 80 * 64
                                                 = 2560 
So the Kinetic energy of the footballer is 2560 joules