The accelerations of a particle as seen from two frames S1 and S2 have equal magnitude \(4\) m/s2.
| 1. | The frames must be at rest with respect to each other. |
| 2. | The frames may be moving with respect to each other but neither should be accelerated with respect to the other. |
| 3. | The acceleration of S2 with respect to S1 may either be zero or \(8\) m/s2. |
| 4. | The acceleration of S2 with respect to S1 may be anything between zero and \(8\) m/s2. |