Answer :

AL2006
Change of PE over a height of 10m = M G H = (10) (9.8) (10) = 980 joules.

When the box hits the bottom, it has 980 joules less PE than it had
before it started dropping. 

(As well as 980 joules more kinetic energy.)
P.E = mgh                           
M= MASS
G= ACCELERATION DUE TO GRAVITY
H = HEIGHT
P.E= 10 * 10 * 10
P.E = 1000J