Physical World Units and Measurements - Result Question 2
2. The density of material in CGS system of units is $4 g / cm^{3}$. In a system of units in which unit of length is $10 cm$ and unit of mass is $100 g$, the value of density of material will be [2011M]
(a) 0.4
(b) 40
(c) 400
(d) 0.04
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Answer:
Correct Answer: 2. (b)
Solution:
- (b) In CGS system, density $d=4 \frac{g}{cm^{3}}$
unit of length $=1 cm$
unit of mass $=1 g$
And in another system of units
The unit of mass is $100 g$ and unit of length is 10 $cm$, so substitute these values
Density $=\frac{4(\frac{100 g}{100})}{(\frac{10}{10} cm)^{3}}=\frac{(\frac{4}{100})}{(\frac{1}{10})^{3}} \frac{(100 g)}{(10 cm)^{3}}$
$=\frac{4}{100} \times(10)^{3} \cdot \frac{100 g}{(10 cm)^{3}}=40$ unit
Apart from fundamental and derived units, we have also used practical units e.g., horse power (h.p.) is a practical units of power. Practical units may or may not belong to a system but can be expressed in any system of units.
