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Question:

Two particles A, B are moving on two concentric circles of radii R1 and R2 with equal angular speed ω. At t=0, their positions and direction of motion are shown in the figure. The relative velocity →uA − →vB at t=π/2ω is given by:

−ω(R1+R2)^i

ω(R1+R2)^i

ω(R2−R1)^i

ω(R1−R2)^i

Solution:

The correct option is D ω(R2−R1)^i θ=ωt=ωπ/2ω=π/2. →VA−→VS=ωR1(−^i)−ωR2(−i) =ω(R2−R1)^i