A swimmer can swim in still water at a rate 4.0 km/h. If he swims in a river flowing at 3.0 km/h and keeps his direction (with respect to water) perpendicular to the current, find his velocity with respect to ground.
A
5.0 km/h
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B
7.0 km/h
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C
9.0 km/h
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D
11.0 km/h
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Solution
The correct option is B 5.0 km/h The velocity of the flow of river with respect to ground is =→vR=3km/h^i
The velocity of swimmer with respect to river=→vSR=4km/h^j
Hence the velocity of swimmer with respect to ground=→vR+→vSR=3km/h^i+4km/h^j
Hence the magnitude of this velocity is √32+42km/h