45.A man can swim at a speed of 3 km/h in stillwater. He Wants to cros

1.	45.A man can swim at a speed of 3 km/h in stillwater. He Wants to cross a 500 m wide riverflowing at 2 km/h. He keeps himself alwaysat an angle of 120Â° with the river flow whileswimming. The time he lakes to cross theriver iS
Answer» given, speed of man, Vm= 3km/hr speed of river, Vr= 2km/hr angle which the man makes with the direction of motion of river = 120 The resultant velocity of man can be calculated by the parallelogram law of vectors as, angle between Vrand VR now time required to cross the river = OB/VR in trianle ABO, angleAOB = 90o- 79o= 11o so, OB = AO/cos11o= 0.5/0.981 = 0.509 sotime required = 0.509/2.6 = 0.196hr = 0.196x60x60 = 705.6s Now the point where he will reach is B,andthe distance of B from A = AB = AOtan11 = 0.097km= 0.097x1000= 97m Like my answer if you find it useful! Wrong answer

45.A man can swim at a speed of 3 km/h in stillwater. He Wants to cross a 500 m wide riverflowing at 2 km/h. He keeps himself alwaysat an angle of 120Â° with the river flow whileswimming. The time he lakes to cross theriver iS

Answer»

given,

speed of man, Vm= 3km/hr

speed of river, Vr= 2km/hr

angle which the man makes with the direction of motion of river = 120

The resultant velocity of man can be calculated by the parallelogram law of vectors as,

angle between Vrand VR

now time required to cross the river = OB/VR

in trianle ABO, angleAOB = 90o- 79o= 11o

so, OB = AO/cos11o= 0.5/0.981 = 0.509

sotime required = 0.509/2.6 = 0.196hr = 0.196x60x60 = 705.6s

Now the point where he will reach is B,andthe distance of B from A = AB = AOtan11 = 0.097km= 0.097x1000= 97m

Like my answer if you find it useful!

Wrong answer

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