An isolated space probe in deep space has no energy exchanges with its external surroundings. Inside the probe, a chemical battery powers an electric motor to spin a heavy internal flywheel. Due to friction in the bearings, some energy is dissipated as thermal energy, raising the temperature of the probe's components.
Which statement correctly describes the energy of this closed system?
The total energy of the system decreases over time because energy is dissipated as thermal energy.
The sum of the energy in the chemical and kinetic stores decreases over time, while the total energy of the system remains constant.
The total energy of the system increases because the flywheel gains kinetic energy.
The total energy of the system remains constant only if the electric motor operates at 100%100\%100% efficiency.
82 exam-style questions on Edexcel GCSE Physics 3.1 Energy stores and calculations. Each one has a worked solution and a mark scheme showing where the marks go.