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Motion in A Plane

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Physics Part I

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Physics

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Rain is falling vertically with a speed of 30 m s-1. A woman rides a bicycle with a speed of 10 m s-1 in the north to south direction. What is the direction in which she should hold her umbrella?

Let, 

vc = Velocity of the cyclist, and

vr = Velocity of falling rain 

The woman must hold her umbrella in the direction of the relative velocity (v) of the rain, in order to protect herself from the rain. 

straight v space equals space straight v subscript straight r space end subscript plus space left parenthesis negative straight v subscript straight c right parenthesis space

space space space equals space 30 space plus space left parenthesis negative 10 right parenthesis space

space space space equals space 20 space straight m divided by straight s space

tan space straight theta space equals fraction numerator space straight v subscript straight c over denominator space straight v subscript straight r space end subscript end fraction space equals fraction numerator space 10 space over denominator 30 end fraction
rightwards double arrow space straight theta space equals space tan to the power of negative 1 end exponent space open parentheses fraction numerator 1 space over denominator 3 end fraction close parentheses space
space space space space space space space space space equals tan to the power of negative 1 end exponent space left parenthesis 0.333 right parenthesis space almost equal to space 18 to the power of 0 space


Therefore, the woman must hold the umbrella towards the south, at an angle of 18o.

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Give three examples of vector quantities.

Force, impulse and momentum.
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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
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