Physics Circle home Student Login

Home›Chapters›Projectile Motion PYQs›Relative Velocity in Two Dimensions›Question 19

JEE Main 2019 (9 Apr, Shift 1) · Relative Velocity in Two Dimensions

Relative Velocity in Two Dimensions question from JEE Main 2019 (9 Apr, Shift 1)

Q19JEE Main 2019 · 9 APR · SHIFT 1Easy

Relative Velocity in Two Dimensions

The stream of a river is flowing with a speed of 2km/h. A swimmer can swim at a speed of 4km/h. What should be the direction of the swimmer with respect to the flow of the river to cross the river straight?

Show answer and solution

Answer: (b)

  1. To cross straight, the upstream component must cancel the flow: vscos⁡θ=−vrv_s\cos\theta = -v_r, with θ\theta measured from the flow.
  2. cos⁡θ=−24=−12⇒θ=120∘\cos\theta = -\frac{2}{4} = -\frac{1}{2} \Rightarrow \theta = 120^\circ
  3. So the answer is (b) 120∘120^\circ.
Report a mistake

More questions on Relative Velocity in Two Dimensions