A particle is under the action of force of constant magnitude. The direction of the force is such that it is always normal to the velocity of the particle. If the motion of the particle is confined to a plane, then:

Explanation

When a particle experiences a force that is always perpendicular to its velocity, the force alters the direction of the velocity without changing its magnitude. This results in a centripetal force that causes the particle to move in a circular path. Hence, the correct answer is that the particle has circular motion.Option A is incorrect because linear motion would require the force to be in the direction of motion, not perpendicular to it. Option C is incorrect because while the magnitude of acceleration is constant, its direction is continuously changing as the particle moves. Option D is incorrect because even though the speed (magnitude of velocity) is constant, the velocity itself is not constant due to the change in direction.