A flywheel energy store is spun by an electric motor. Energy transferred to the kinetic store of the flywheel is useful.
An engineer tests the flywheel with dry bearings and then with lubricant added to the bearings. The total input energy transfer is the same in both tests.
| Condition of bearings | Total input energy transfer in kJ | Useful output energy transfer in kJ |
|---|---|---|
| Dry | 24.0 | 14.4 |
| Lubricated | 24.0 | 18.0 |
Calculate the energy dissipated in each test.
Explain how adding lubricant to the bearings affected the efficiency of the energy transfer.
104 exam-style questions on AQA GCSE Physics 1.2 Conservation and dissipation of energy, covering 1.2.1 Energy transfers in a system and 1.2.2 Efficiency. Each one has a worked solution and a mark scheme showing where the marks go.