47. The electric field is formed by a positively charged infinitely long thread. Moving under the action of this field along a field line from a point located at a distance x1 = 1 cm from the filament to a point x2 = 4 cm, the α particle has changed its speed from 2 ∙ 105 to 3 ∙ 106 m / s. Find the linear charge density on the thread.

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)