You serve a volley ball with a mass of 2.1 kg. the ball leaves your hand with the speed of 30 m/s. the ball has energy. calculate it

Kinetic energy.
To calculate you have to use the equation for kinetic energy
\frac{1}{2} m v ^{2}
= 1/2 m v^2
= 1/2 *  2.1 kg * (30 m/s)^2
= 945 kg m^2/s^2
= 945 Joule

Because it was a dramatically big guy