Motion in a Plane
Class 11 · Motion in a Plane
Vector Addition
Triangle and parallelogram law — add two vectors and read |R| and angle θ live.
Key Notes
01
Triangle law: place tail of B at head of A; resultant R goes from tail of A to head of B.
02
Parallelogram law: place both tails together; R is the diagonal of the parallelogram.
03
R² = A² + B² + 2AB cosθ, where θ is the angle between them.
04
Vectors commute: A + B = B + A.
05
If θ = 0: R = A + B (max). If θ = 180°: R = |A − B| (min). If θ = 90°: R = √(A² + B²).
Formulas
Resultant magnitude
Law of cosines for vector addition.
Direction of R
Angle of R with A.
Important Points
Unit vectors simplify addition: A + B = (Aₓ+Bₓ)î + (Aᵧ+Bᵧ)ĵ.
Vector Addition notes from sciphylab (also known as SciPhy, SciPhy Lab, SciPhy Labs, Physics Lab). Class 11 physics revision for JEE Mains, JEE Advanced, NEET UG, AP Physics 1/2/C, SAT, and CUET-UG.