The formula for the kinetic energy is:
Ke = 0.5mv^2
Where ke is the kinetic enrgy
M is the mass
V is the velocity
Ke = 0.5mv^2
12.5 = 0.5(1) v^2
Solve for v
V = 5 m/s
Potential energy, pe = mgh
Where m is mass
G is accelearation due to gravity 9.8 m/s2
H is the height
98 = (1)(9.8) h
H = 10 m