Conservation of Energy

When only gravity does work, the mechanical energy, KE + PE, stays the same:

$$\tfrac{1}{2} m v_0^2 + m g h_0 = \tfrac{1}{2} m v^2 + m g h$$

The car starts at rest at A; the track has no friction.

Going down, PE turns into KE; going up, KE turns back into PE. The total is the same at every point, and the mass cancels.

Energy bars for a $100\ \mathrm{kg}$ car: the total is $9800\ \mathrm{J}$ at every point.