Calculating New Vector Components

[josh84]

Homework Statement

A certain vector in the xy plane has an x component of 4 and a y component of 10. It is rotated in the xy plane so its x component is doubled. Its new y component is about:
A. 20
B.7.2
C.5.0
D.4.5
E.2.2

Homework Equations

The Attempt at a Solution

 

[hage567]

You must show some work. What do you know about vectors? Do you know how to find the magnitude?