A platform in a mine is moving upwards. The forces acting on it are recorded during three consecutive intervals. The platform remains moving upwards throughout these intervals.
| Interval | Upward force | Downward force |
|---|---|---|
| 1 | 4600 N | 4600 N |
| 2 | 4000 N | 4600 N |
| 3 | 4600 N | 4600 N |
Calculate the size of the resultant force on the platform during interval 2.
Explain how the speed changes during interval 2 and compare the speed at the end of interval 3 with the speed at the start of interval 1.