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← JEE Advanced 2017 · Paper 2
PhysicsSingle correct+3 / -1Question 5 of 54

JEE Advanced 2017 · Paper 2, Physics question 5

Three vectors P⃗\vec{P}, Q⃗\vec{Q} and R⃗\vec{R} are shown in the figure. Let SS be any point on the vector R⃗\vec{R}. The distance between the points PP and SS is b∣R⃗∣b|\vec{R}|. The general relation among vectors P⃗\vec{P}, Q⃗\vec{Q} and S⃗\vec{S} is

From the origin O, vectors P⃗ (to point P, steeper) and Q⃗ (to point Q, shallower) are drawn; R⃗ = Q⃗ − P⃗ runs from P to Q. A point S on R⃗ is at distance b|R⃗| from P, and S⃗ runs from O to S.
Choose one option
Answer and worked solution

Official answer: A

SS lies on R⃗=Q⃗−P⃗\vec R=\vec Q-\vec P, a distance b∣R⃗∣b|\vec R| from PP. So
S⃗=P⃗+bR⃗=P⃗+b(Q⃗−P⃗)=(1−b)P⃗+bQ⃗.\vec S=\vec P+b\vec R=\vec P+b(\vec Q-\vec P)=(1-b)\vec P+b\vec Q.

(A)

Topics:Vectors