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Class 10 Class 12
A man can swim with a speed of 4.0 km/hr in still water. How long does he take to cross the river 1.0 km wide if the river flows steadily at 3.0 km/hr and he makes his strokes normal to the river current? How far down the river does he go when he reaches the other bank?

Rate of flow of swimmer in the still water = 4.0 km/hr

Width of the river = 1.0 km

Rate of flow of river = 3.0 km/hr

Since the swimmer dives in the river normal to the flow of river, therefore time taken by swimmer to cross the river is,

In this time the swimmer will also go down the river by distance BC due to river current.

∴ Distance of the river travelled by the swimmer when he reaches the other bank is given by,

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What is a scalar quantity?

A physical quantity that requires only magnitude for its complete specification is called a scalar quantity.
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What is a vector quantity?

A physical quantity that requires direction along with magnitude, for its complete specification is called a vector quantity.
835 Views

Give three examples of vector quantities.

Force, impulse and momentum.
865 Views

What are the basic characteristics that a quantity must possess so that it may be a vector quantity?

A quantity must possess the direction and must follow the vector axioms. Any quantity that follows the vector axioms are classified as vectors.

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Give three examples of scalar quantities.

Mass, temperature and energy
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