A man starts at point on a riverbank, tries to swim at an angle of π/3 with riverbank with speed u, reaches a point downstream on the other bank and runs to the point exactly opposite to where he started with speed 2u all in 30 seconds. If river is flowing with a speed u/2, find u in m/s (upto two decimal places)
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Explanation:
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Class 11
>>Physics
>>Motion in a Plane
>>Relative Motion in 2 Dimension
>>A person swims in a river aiming to reac
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A person swims in a river aiming to reach exactly on the opposite point on the bank of river. His speed of swimming is 0.5 m/s at an angle of 120
∘
with the direction of flow of water. The speed of water is
Medium
Solution
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Correct option is C)
The angle made by the person swimming with the direction perpendicular to the flow of water is 120
∘
−90
∘
=30
∘
To reach the point B, drift must be zero, i.e., the relative velocity of boat w.r.t. river, v
br
, should be along perpendicular direction.
Equating the component of velocity along horizontal direction to zero,
v
b
sinθ−v
r
=0
sin30
∘
=
0.5
v
water