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

Which statement is true? a) the work done to lift an object 6 meters is greater than the gravitational potential energy it gains. b) the work required to push an object is less than the work required to pull an object the same distance. c) the work required to raise an object to a height is equal to the gravitational potential energy the object gains. d) the work done against gravity to lift an object straight up is greater than the work required to roll it up a ramp.