KE = (1/2) (mass) (speed)²
KE = (1/2) (20 kg) (40 m/s)²
KE = (1/2) (20 kg) (1,600 m²/s²)
KE = (10 kg) (1,600 m²/s²)
KE = 16,000 Joules
Using the kinematic equation d = V_0 * t + 1/2 * a * t^2, where d is height you can rewrite this to be d = 1/2*g*t^2 or 4.9t^2
g = a because this is a free fall
d = 1/2 * 9.81m/s^2 * 2.5^2
d = 30.65625m
d = 30.7m
No, one more group must get the same result as the other group. This will make it more reliable and reproducible.