Apply the law of conservation of energy and describe the energy transformations that occur as you coast down a long hill on a bicycle and then apply the brakes to make the bike stop at the bottom.
a roller coaster is at the top 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?

As you coast down a long hill on your bicycle, potential energy from your height is converted to kinetic energy as you and your bike are pulled downward by gravity along the slope of the hill. While there is air resistance and friction slowing you down by a little bit, your speed increases gradually until you apply the brakes, causing enough friction to slow yourself and the bike to a stop at the bottom.

A roller coaster will have higher kinetic energy at the lower hill because it will have already been moving as opposed to the initial hill. But I'm not one hundred percent certain. You can always google this stuff, but I do know for sure that at the first hill, the roller coaster will have higher potential energy.
Hope this helps!