JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Kinematics

A person is swimming with a speed of

10 m / s

at an angle of

12 0^{0}

with the flow and reaches to a point directly opposite on the other side of the river. The speed of the flow is 'x'

m / s

. The value of 'x' to the nearest integer is ______

Answer: 5

Solution

The swimmer's velocity makes

12 0^{\circ}

with the direction of flow, so its component along the flow is

10 cos 12 0^{\circ} = - 5

m/s, that is

5

m/s directed upstream. Reaching the point directly opposite means the resultant velocity has no component along the flow, so this upstream component must exactly cancel the velocity of the stream:

v_{flow} = 10 cos 6 0^{\circ} = 10 \times \frac{1}{2} = 5 m/s

The speed of the flow is

5

m/s.

JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Integer answer

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