Question

1 joule is equal to

• A. ${10}^{5}erg$
• B. ${10}^{6}erg$
• C. ${10}^{7}erg$
• D. ${10}^{9}erg$

Answer 1

The correct option is C ${10}^{7}erg$

$\begin{array}{ccc}\text{Quantity}& \text{SI unit}& \text{CGS unit}\\ \text{Length}& \text{m}& \text{cm}\\ \text{Mass}& \text{kg}& \text{g}\\ \text{Time}& \text{s}& \text{s}\end{array}$

In SI unit:

$1Joule=1kg{m}^2{s}^{–2}\text{In CGS units:}1Joule=1kg{m}^2{s}^{–2}=1\left(1000g\right)\times (100cm{)}^2\times (1s{)}^{–2}(\because 1kg=1000g,1m=100cm)\Rightarrow 1Joule=1000\times {10}^{4}gc{m}^2{s}^{–2}\Rightarrow 1Joule={10}^{7}gc{m}^2{s}^{–2}\Rightarrow 1Joule={10}^{7}erg(\because 1gc{m}^2{s}^{–2}=1erg)$

Hence, the correct answer is option (c).