A charged particle enters a region in which it is subject to a resistive force whose magnitude is directly proportional to the particle’s speed. The particle comes to rest at a point 20.0 cm away from the entry point. However, if a uniform magnetic field, perpendicular to the particle’s velocity, exists in the region, the particle stops 12.0 cm away from the entry point. How far from the entry point would the particle stop if the magnitude of the magnetic field is halved?

In all cases, the particle enters the region with the same speed.

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