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Class 10 Class 12

A stream of width d is flowing with velocity v. A person who can swim with speed V relative to water wishes to row straight across it. In what direction should he strike out and how long would it take him to cross the stream?

To row straight across the stream, the person must strike out at angle θ upstream, such that the resultant R of his own velocity and velocity of stream is perpendicular to velocity of stream.

∴

∴

The swimmer should dive at an angle  with normal to river and upstream.

Now the resultant velocity of swimmer and the stream is,

Therefore the time taken by swimmer to cross the river is,

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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.
1212 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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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.
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