A rolleroaster is at the stop of a hill and rolls to the top of a lower hill. If mechanical energy is constant, then on the top of which hill is the kinetic energy from the roller coaster's motion greater?

Kinetic energy will be greater on the top of lower hill and potential energy will be greater on the top of tallest hill.  

Explanation: Let us consider that the height of tallest peak is H and that of lower peak is h.

So according to the conservation of mechanical energy, total energy at the top of both the peaks should be equal.

Mechanical energy at top of tallest peak = Total energy at lower peak

Total mechanical energy = Potential energy + Kinetic energy

PE is due to the virtue of position or height and defined as

PE = =

Greater the height of peak greater will be the potential energy and to conserve the mechanical energy smaller will be the kinetic energy.

Hence,

Kinetic energy will be greater on the top of lower hill and potential energy will be greater on the top of tallest hill.

an obstruction

it takes about 30 days for it to break down