Question
A certain vector in the xy-plane has an x-component of 4 m and a y-component of 10 m. It is then rotated in the xy-plane so that its x-component is doubled. Then, its new y-component is (approximately)
20 m
7.2 m
5.0 m
4.5 m
Solution
B.
7.2 m
Here, A= 4 i + 10 j
=
m
Now, according to question,
A = 8 i + n j
⇒
Squaring on both sides
116 = 64 + n2
⇒
n = 7.2 m