A roller coaster car starts from rest at the top of a hill and rolls down to the bottom. Explain what happens to the energy stores of the roller coaster car as it travels from the top to the bottom of the hill, assuming there is no friction.

Edexcel GCSE Physics (1PH0) — 3.1 Conservation of energy · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A roller coaster car is released from rest at the top of a hill. The car rolls down to the bottom of the hill without any friction acting on it.

Model answer (4 marks)

The car has gravitational potential energy (GPE) at the top of the hill.
As it moves down, the GPE decreases.
The lost GPE is transferred to the car’s kinetic energy.
With no friction, no energy is dissipated, so the total energy remains constant.

Examiner tips

  • Use the exact phrase "gravitational potential energy" and "kinetic energy". Show the energy transfer sequence. Mention that the system is closed and energy is conserved. Keep the answer short and to the point.

Common mistakes

  • Writing that energy is lost or wasted. Forgetting to mention the conservation of total energy. Using vague terms like "energy changes" instead of specifying GPE and KE.

Mark scheme (4 marks)

  1. The car has gravitational potential energy (GPE) at the top of the hill
  2. As the car moves down the hill, the gravitational potential energy decreases / is transferred
  3. The gravitational potential energy is transferred to the kinetic energy store
  4. Because there is no friction, no energy is dissipated / wasted, so the total energy of the closed system remains constant / is conserved

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