Question

a roller coaster car traveling uphill has an initial potential energy of 500 j and an initial kinetic energy of 2500 j. once it has reached the top of the hill, its final potential energy is 2500 j and its final kinetic energy is 0 j.
how can the \lost\ energy most likely be accounted for?
there was 500 j of work done by friction as the car traveled up the hill.
the car lost 500 j of chemical energy as fuel was burned to pull the car up the hill.
the car was only able to gain a maximum potential energy equal to the initial kinetic energy because it stopped at the top of the hill.
the weight of the car caused it to slow down, decreasing its total mechanical energy.
pe_f = 2500 j
ke_f = 0 j

Explanation:

Step1: Calculate initial total energy

Initial total energy = Initial PE + Initial KE = 500 J + 2500 J = 3000 J

Step2: Calculate final total energy

Final total energy = Final PE + Final KE = 2500 J + 0 J = 2500 J

Step3: Find energy difference

Energy lost = Initial total - Final total = 3000 J - 2500 J = 500 J

Step4: Identify energy loss cause

Friction dissipates mechanical energy as heat; other options are incorrect (no fuel burn, weight doesn’t reduce total energy, PE gain isn’t limited to initial KE).

Answer:

A. There was 500 J of work done by friction as the car traveled up the hill.