basic physics question?

[WestWind]

This statement is false: If the net force acting on an object is in the positive x-direction, the object moves only in the positive x-direction.

Can someone explain why this is false? My book doesn't really explain it and I'm kinda confused. Just an example of why it's not right would be helpful.

[Chris C]

Just because the net force, meaning the final resultant, is in the +x direction, does not mean that the object did not move -and then -. It could have moved x -3, then x +6. So the net force was +3x. It could have also moved in the y, but those movements countered themselves

[Venus]

say a body was previously acted by a force in y direction which gave the body a constant velocity in that direction. now if net force this very second acts on the already moving body in x direction the resulting direction will be x-y and not x. the statement would be true if it says 'on a stationary body'.