a swimmer wants to cross a river straight he swim at 5kmhr

A swimmer wants to cross a river straight. He swim at $$5\,km/hr$$ in still water. A river $$1\,km$$ wide flows at the rate of $$3\,km/hr.$$ Which of the following figure shows the correct direction for the swimmer along which he should strike?
($${V_s} \to $$ velocity of swimmer, $${V_r} \to $$ velocity of river, $$V \to $$ resultant velocity)

Answer : Kinematics mcq option image

Solution :
The swimmer will cross straight if the resultant velocity of river flow and swimmer acts perpendicular to the direction of river flow. It will be so if the swimmer moves making an angle $$\alpha $$ with the upstream. i.e. goes along $$OB.$$
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Basic Physics >> Kinematics

Releted Question 1

A river is flowing from west to east at a speed of $$5$$ metres per minute. A man on the south bank of the river, capable of swimming at $$10$$ metres per minute in still water, wants to swim across the river in the shortest time. He should swim in a direction-

A. Due north

B. $${30^ \circ }$$ East of north

C. $${30^ \circ }$$ West of north

D. $${60^ \circ }$$ East of north

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Releted Question 2

A boat which has a speed of $$5 km/hr$$ in still water crosses a river of width $$1 \,km$$ along the shortest possible path in $$15 \,minutes.$$ The velocity of the river water in $$km/hr$$ is-

A. 1

B. 3

C. 4

D. $$\sqrt {41} $$

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Releted Question 3

In $$1.0\,s,$$ a particle goes from point $$A$$ to point $$B,$$ moving in a semicircle of radius $$1.0 \,m$$ (see Figure). The magnitude of the average velocity-

A. $$3.14 \,m/s$$

B. $$2.0 \,m/s$$

C. $$1.0 \,m/s$$

D. Zero

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Releted Question 4

A ball is dropped vertically from a height $$d$$ above the ground. It hits the ground and bounces up vertically to a height $$\frac{d}{2}.$$ Neglecting subsequent motion and air resistance, its velocity $$v$$ varies with the height $$h$$ above the ground as-

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Releted MCQ Question on
Basic Physics >> Kinematics

A river is flowing from west to east at a speed of $$5$$ metres per minute. A man on the south bank of the river, capable of swimming at $$10$$ metres per minute in still water, wants to swim across the river in the shortest time. He should swim in a direction-

A boat which has a speed of $$5 km/hr$$ in still water crosses a river of width $$1 \,km$$ along the shortest possible path in $$15 \,minutes.$$ The velocity of the river water in $$km/hr$$ is-

In $$1.0\,s,$$ a particle goes from point $$A$$ to point $$B,$$ moving in a semicircle of radius $$1.0 \,m$$ (see Figure). The magnitude of the average velocity-

A ball is dropped vertically from a height $$d$$ above the ground. It hits the ground and bounces up vertically to a height $$\frac{d}{2}.$$ Neglecting subsequent motion and air resistance, its velocity $$v$$ varies with the height $$h$$ above the ground as-

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Releted MCQ Question on Basic Physics >> Kinematics

A river is flowing from west to east at a speed of $$5$$ metres per minute. A man on the south bank of the river, capable of swimming at $$10$$ metres per minute in still water, wants to swim across the river in the shortest time. He should swim in a direction-

A boat which has a speed of $$5 km/hr$$ in still water crosses a river of width $$1 \,km$$ along the shortest possible path in $$15 \,minutes.$$ The velocity of the river water in $$km/hr$$ is-

In $$1.0\,s,$$ a particle goes from point $$A$$ to point $$B,$$ moving in a semicircle of radius $$1.0 \,m$$ (see Figure). The magnitude of the average velocity-

A ball is dropped vertically from a height $$d$$ above the ground. It hits the ground and bounces up vertically to a height $$\frac{d}{2}.$$ Neglecting subsequent motion and air resistance, its velocity $$v$$ varies with the height $$h$$ above the ground as-

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