A vector in the plane makes an angle of with the -axis. The magnitude of the -component of the vector is . The magnitude of the -component of the vector will be
- A
- B
- C
- D
A vector in the plane makes an angle of with the -axis. The magnitude of the -component of the vector is . The magnitude of the -component of the vector will be
Correct answer:A
Standard Method
Given: A vector makes an angle of with the -axis, and its -component is .
Find: The magnitude of the -component.
If a vector of magnitude makes an angle with the -axis, then
Using the given values,
Since
we get
Cancelling ,
Now the magnitude of the -component is
Therefore, the magnitude of the -component is . The correct option is A.
Component Ratio Trick
Given: The angle is measured from the -axis.
Find: The -component.
When the angle is measured from the -axis,
So,
Hence,
Therefore, the magnitude of the -component is .
Using and as if the angle were measured from the -axis. This is wrong because the given angle is with the -axis. Use and instead.
Treating the given as the vector magnitude instead of the -component. This is wrong because the problem explicitly gives only one component. First find or use the component ratio correctly.
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