Units and Measurement

Physics Part I

Physics

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State the number of significant figures in the following :

a) 0.007 m^{2}

b) 2.64 10^{24}kg

(c) 0.2370 g cm^{–3}(d) 6.320 J

(e) 6.032 N m^{–2 }

(f) 0.0006032 m^{2}

a) 0.007 m

b) 2.64 10

(c) 0.2370 g cm

(e) 6.032 N m

(f) 0.0006032 m

a) 1

The given quantity is 0.007 m^{2}

If the number is less than one, then all zeros on the right of the decimal point (but left to the first non-zero) are insignificant. This means that here, two zeros after the decimal are not significant. Hence, only 7 is a significant figure in this quantity.

b) 3Here, the power of 10 is irrelevant for the determination of significant figures. Hence, all the digits are significant figures.

c) 4

d) 4

e) 4

f) 4

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Define unit.

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

Example: Unit of time is second.

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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.

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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.

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What is measurement?

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