The vector has components +5 and +7 along the x and y axes respectively. If the vector is now rotated 90 degrees counterclockwise relative to the original axes, the vector's components are now
A)−7; −5.
B)7; −5.
C)−7; 5.
D)7; 5.
E)7; 0.

Question

The vector  has components +5 and +7 along the x and y axes respectively. If the vector is now rotated 90 degrees counterclockwise relative to the original axes, the vector's components are now
A)−7; −5. 
B)7; −5. 
C)−7; 5. 
D)7; 5. 
E)7; 0.

Quizplus · Accepted Answer

When a vector is rotated 90 degrees counterclockwise, its x component becomes its negative y component, and its y component becomes its positive x component.

So, the new components of the vector are -7 along the x axis and +5 along the y axis. Therefore, the answer is C, (-7,5).

The Vector Has Components +5 and +7 Along the X