Question

A proton is released from rest at the dot. What happens to the proton afterward?

1) It moves in a straight line
2) It moves in a circular path
3) It remains at rest
4) It moves randomly

Answer 1

A proton released in a magnetic field will execute circular motion because the magnetic force acts as a centripetal force, which is always perpendicular to the velocity of the proton. The radius of the proton's path can be calculated using kinematic relations.

Step-by-step explanation:

The question is about the motion of a proton after it is released from rest in the presence of a magnetic field. When a proton is released, if it experiences a magnetic field which is perpendicular to the velocity of the proton, that proton will execute circular motion. This is because the magnetic force acts as a centripetal force, which is always perpendicular to the velocity of the proton, causing it to move in a circular path without changing the magnitude of its velocity. This is in accordance with the right-hand rule of magnetic forces on moving charges.

The radius of the circular path can be determined using kinematic relations, and in the context of a proton entering a magnetic field perpendicularly, the proton will move in a circular path. This is demonstrated in Exercise 29, where different scenarios involving protons moving in magnetic fields are considered. The trajectory and other properties such as the angular momentum of the proton can be calculated if additional information is provided, as shown in CHECK YOUR UNDERSTANDING 11.2 and EXAMPLE 4.11