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Class 10 Class 12
A river 100 m wide is running downwards at the rate of 1 km per hour and a swimmer who can swim at the rate of 3·6 km/hr wishes to reach a point just opposite. Along which direction should he strike and how long will he take to cross the river?

Given,

Width of the river = 100 m

Rate of flow of river = 1 km/hr

Rate of flow of swimmer = 3.6 km/hr

Let the swimmer dive at an angle  as shown in figure to reach the point B directly opposite to A.

From the fig., we have

∴

Therefore, the swimmer should dive at angle (90 + 16·14) =106·14° with the direction of flow.

Now,

Time taken to cross the river, t =

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Give three examples of scalar quantities.

Mass, temperature and energy
769 Views

What is a scalar quantity?

A physical quantity that requires only magnitude for its complete specification is called a scalar quantity.
1212 Views

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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