In an inertial frame of reference, a series of experiments is conducted. In each experiment, two or three forces are applied to an object. The magnitudes of these forces are given. No other forces are acting on the object. In which cases may the object possibly move at a constant velocity of 256m/s?

1. 2 N; 2 N

2. 200 N; 200 N

3. 200 N; 201 N

4. 2 N; 2 N; 4 N

5. 2 N; 2 N; 2 N

6. 2 N; 2 N; 3 N

7. 2 N; 2 N; 5 N

8. 200 N; 200 N; 5 N