SAT Subject Physics Practice Question 332: Answer and Explanation
The two-dimensional cube in the diagram above has charged objects placed at the corners as shown. An electron that is free to move is placed at the exact center of the cube. In which direction will the electron move?
A. It will move toward A.
B. It will move toward B.
C. It will move toward C.
D. It will move toward D.
E. It will remain stationary.
Correct Answer: D
The correct answer is (D). The electron will be repelled toward point D by the β (beta) particle located at point B. The two alpha particles located at points A and C exert equal attractive forces force on the electron, which keep the electron on a straight line toward the proton at D.