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MCAT Physics Question – Ions

Ions X, Y, and Z are initially held fixed in the orientation shown below:

MCAT Sample Question -- Physics
Which of the following vectors corresponds to the direction ion Z will move immediately after it is released from its fixed position?


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Ion X (+2e) pushes ion Z (+e) down and to the right. Ion Y (-e) pulls ion Z (+e) down and to the left. The magnitude of the force created by ion X (+2e) is twice that of the force created by ion Y (-e) due to the difference in charge. The relative forces that act on ion Z are shown below.

The resultant force from the addition of ZX and ZY is shown as vector ZX+Y, which causes ion Z (+e) to move down and to the right. Thus, answer choice is D is correct.

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