Let's determine if all the hills on a roller coaster can be the same height.
By applying the conservation of energy, a roller coaster can move up to a height which is equal to the height it went down before.
In a roller coaster, the first hills are always the highest, while the subsequent hills will have decreasing heights.
This is due to a decrease in the total mechanical energy of the system caused by friction.
Therefore, we can say the hills on a roller coaster are not of the same height due to decrease in total mechanical energy caused by lost to friction.
ANSWER:
The hills on a roller coaster are not of the same height due to decrease in total mechanical energy caused by lost to friction.