Vo = 0m / s
Vf = <img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B180km%7D%7B1h%7D%2A%20%5Cfrac%7B1000m%7D%7B1km%7D%2A%5Cfrac%7B1h%7D%7B3600s%7D%3D%2050m%2Fs" />
X = 500m
<img src="https://tex.z-dn.net/?f=Vf%5E%7B2%7D%3DVo%5E%7B2%7D%2B2.a.x%20" />
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7BVf%5E%7B2%7D%7D%7B2.a%7D%20%3Da%20" />
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B%2850m%2Fs%29%5E%7B2%7D%20%7D%7B2%28500m%29%7D%20%3Da" />
<img src="https://tex.z-dn.net/?f=%5Cfrac%7B2500m%5E%7B2%7D%2Fs%5E%7B2%7D%20%7D%7B1000m%7D%20%3Da" />
<img src="https://tex.z-dn.net/?f=2%2C5m%2Fs%5E%7B2%7D%20%3Da" />
<img src="https://tex.z-dn.net/?f=a%3D%20%5Cfrac%7BVf-Vo%7D%7Bt%7D%20" />
<img src="https://tex.z-dn.net/?f=t%3D%20%5Cfrac%7BVf-Vo%7D%7Ba%7D%20" />
<img src="https://tex.z-dn.net/?f=t%3D%5Cfrac%7B50m%2Fs-0m%2Fs%7D%7B2%2C5m%2Fs%5E%7B2%7D%20%7D%20" />
<img src="https://tex.z-dn.net/?f=t%3D20s" />.