Question
Physics Question on Newtons Laws of Motion
Two forces P and Q of magnitude 2F and 3F, respectively, are at an angle θ with each other. If the force Q is doubled, then their resultant also gets doubled. Then, the angle is :
A
30∘
B
60∘
C
90∘
D
120∘
Answer
120∘
Explanation
Solution
4F2+9F2+12F2cosθ=R2
4F2+36F2+24F2cosθ=4R2
4F2+36F2+24F2cosθ
=4(13F2+12F2cosθ)=52F2+48F2cosθ
cosθ=24F212F2=−21