Since the energy is conserved, we can write the following equations:
[tex]\begin{gathered} E_m=E_k+E_p \\ E_k=\frac{mv^2}{2} \\ E_p=mgh \end{gathered}[/tex]
Where Em is the mechanical energy, Ek is the kinetic energy and Ep is the potential energy.
The kinetic energy is related to the velocity, and the potential energy is related to the height.
When the roller coaster goes down, the potential energy is converted into kinetic energy.
That means the height decreases (and so do the potential energy), but the velocity increases (and so do the kinetic energy).
Therefore the correct option is the sixth one (Both B and D).
