Kinetic energy at the bottom position is equal to the potential energy at the starting position.


This potential energy is  m*g*(1.50-0.80) = 0.5*10*0.7 = 3.5 kg*(m/s^2)*m = 3.5 joules.


Here 0.5 is the mass of 500 grams, expressed in kilograms;

     g = 10 m/s^2  is the gravity acceleration;

     1.50-0.80 = 0.7  is the difference of heights, expressed in meters.


Two energies, potential and kinetic, are equal due to mechanical energy conservation law.