Debemos suponer que la velocidad inicial es cero ya que se deja caer y la aceleracion sera la gravedad
<img src="https://tex.z-dn.net/?f=v%20f%5E%7B2%7D%3D%20vi%5E%7B2%7D%20%2B%202a%20h%20" />
<img src="https://tex.z-dn.net/?f=v%20f%5E%7B2%7D%3D%280%29%20%5E%7B2%7D%20%2B%202%289.8m%2F%20s%5E%7B2%7D%29%2858m%29%20%20%20" />
<img src="https://tex.z-dn.net/?f=v%20f%5E%7B2%7D%20%3D11368%20%20m%5E%7B2%7D%20%2F%20s%5E%7B2%7D%20" />
<img src="https://tex.z-dn.net/?f=vf%3D%20%5Csqrt%7B11368%20m%5E%7B2%7D%2F%20s%5E%7B2%7D%20%20%7D%20" />
<img src="https://tex.z-dn.net/?f=vf%3D33.71m%2Fs" />
para calcular el tiempo
<img src="https://tex.z-dn.net/?f=vf%3Dvi%2Bat" />
<img src="https://tex.z-dn.net/?f=33.71%20m%2Fs%3D0%2B%289.8m%2F%20s%5E%7B2%7D%29t%20" />
<img src="https://tex.z-dn.net/?f=t%3D%20%5Cfrac%7B33.71m%2Fs%7D%7B9.8m%2F%20s%5E%7B2%7D%20%7D%3D3.44s%20" />.