Question

A roller coaster starts from rest at the top of a 20-m (point A) hill as shown in the diagram. Find the velocity of the roller coaster at point B using the principle of conservation of mechanical energy. 

Answer 1

$$0.5mv^2=mgh\\v^2=2gh\\v^2=2(9.8)(20)\\v=19.8\frac{m}{s}$$