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.