A computational model predicts the speed of a roller coaster car at different heights given its speed at the lowest height of its journey, which is at ground level. The speed at the lowest point is 30 m/s. What is the prediction for its speed when it is at a height of 20 m? A. 22.5 m/s
B. 37.5 m/s
C. 18.8 m/s
D. 15.9 m/s

the answers, the correct one is A   v= 22.5 m/s

Explanation:

We can solve this problem using the concepts of conservation of mechanical energy

Starting point. Lowest point of the trajectory

       Em₀ = K = ½ m v₀²

Final point. When it is at a height of y = 20 m

        = K + U = ½ m v² + mg y

how energy is conserved

         Emo = Emf

         ½ m v₀² = ½ m v² + m g y

         v² = v₀² + 2 g y

let's calculate

         v²2 = 30 2 + 2 9.8 20

         v² = 508

         v²= ra 508

         v² = 22.54 m / s

When checking the answers, the correct one is A