Answer:
5.6 m/s
Explanation:
m = 0.25 kg, h = 2 m
initail energy = mgh = 0.25 * 9.81 * 2 = 4.91 J
80% of 4.91 J converted to final kinetic energy mv^2/2
so 0.8 * 4.91 = 0.25*v^2/2
v^2 = 2*0.8*4.91/0.25 = 31.4
v = 5.6 m/s
