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99 Percentile Qs Bank for JEE MainPhysicsMotion in Two Dimensions

Two cars A and B are moving with speeds v_A=120 ~km / h and v_B=50 ~km / h respectively in the directions as indicated by the arrow in the figure below. What is the relative speed of the car B with respect to car A ?

Options

  1. A70 ~km / h
  2. B120 ~km / h
  3. C130 ~km / h
  4. D170 ~km / h

Correct answer

C. 130 ~km / h

Step-by-step solution

The given situation is shown in the following figure Speed of car A , v_A=120 ~km / h v _A=-120 i Speed of car B , v_B=50 ~km / h v _B=-50 j Relative speed of the car B w.r.t. car A , v _ B A = v _B- v _A=-50 j -(-120 i )=-50 j +120 i =120 i -50 j | v _ B A |= (120)^2+(-50)^2 = 16900 =130 ~km / h

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