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Units and Measurement

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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

Just as precise measurements are necessary in science, it is equally important to be  able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity) :

(b) the mass of an elephant


Consider a ship of known base area floating in the sea. 


Let space it apostrophe straight s space depth space in space sea space equals space straight d subscript 1 space

Volume space of space water space displaced space by space ship space is comma space straight V subscript straight b equals Ad subscript 1

Now comma space move space an space elephant space on space the space ship. space

Let space the space dpeth space of space the space ship space be space now space straight d subscript 2 space

Vol. space of space water space displaced space by space the space ship
with space elephant space on space board comma space straight V subscript be space equals space Ad subscript 2 space

Vol. space of space water space displaced space by space elephant space equals space Ad subscript 2 space minus Ad subscript 1 space

Density space of space water space equals space straight D space

Mass space of space elephant space equals space AD space left parenthesis straight d subscript 2 space minus space straight d subscript 1 right parenthesis
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What is the need of measurement?

To get the complete knowledge of any physical quantity, measurement is needed. Measurement of any physical quantity involves comparison with a certain basic, arbitrarily chosen, internationally accepted reference standard called unit. Knowledge without measurement is incomplete and unsatisfactory. 
825 Views

Define physical quantity.

 


A measurable quantity in terms of which laws of Physics can be expressed is called physical quantity.

The result of a measurement of a physical quantity is expressed by a number accompanied by a unit.


878 Views

What is measurement?

Measurement is the process of attaching a numeric value to an aspect of a natural phenomenon. Measurement is making the quantitative knowledge of a physical quantity. 
1289 Views

Define unit.

The quantity used as a standard of measurement is called unit. 

Example: Unit of time is second. 

1172 Views

Give four examples of physical quantities.

Examples of Physical quantitie are force, mass, density and power.
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