Final answer:
The magnetic force on a positively charged particle moving west in a region where the magnetic field points north is south.
Step-by-step explanation:
The direction of the magnetic force on a positively charged particle moving west in a region where the magnetic field points north is south. This can be explained by the right-hand rule, which states that when you point the thumb of your right hand in the direction of the velocity of a positively charged particle and curl your fingers in the direction of the magnetic field, the palm of your hand will face in the direction of the magnetic force. In this case, when you point your thumb west and curl your fingers north, your palm will face south, indicating the direction of the magnetic force.