Gravitational potential energy changes into kineticenergy. The equation for gravitational potential energy is GPE = mgh, where m is the mass in kilograms, g is the acceleration due to gravity (9.8 on Earth), and h is the height above the ground in meters.
GPE = mgh
GPE = (0.5 kg) ( 9.8 m/s^2) (2.0 m)
GPE = 9.8 J