SAT Subject Physics Practice Question 94: Answer and Explanation

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Question: 94

4. In the figure below, what must be the direction of the particle’s velocity, v ?

A. To the right
B. Downward, in the plane of the page
C. Upward, in the plane of the page
D. Out of the plane of the page
E. Into the plane of the page

Correct Answer: E

Explanation:

Since FB is always perpendicular to v, v cannot be upward or downward in the plane of the page; this eliminates B and C. The velocity vector also cannot be to the right, as it is in A, since then v would be antiparallel to B, and FB would be zero. Using the right-hand rule, v must be into the plane of the page.

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