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Work, Power And Energy — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceWork, Power And Energy3 Marks
Question
When water is flowing through a pipe, then its velocity changes by $5\%$. Find the change in percentage, in the power of water.
✓

Answer

we know $\text{Powe}=\frac{\text{work}}{\text{time}}$ also work = change in $KE$ let power in $2nd$ case be $P_2$ P in $1st$ case $=\frac{\frac{1}{2}}{\frac{\text{mv}^2}{\text{time}}}$
$\text{P}_2=\frac{1}{2}\text{m}\Big(\frac{105}{100}\Big)\text{v}\Big(\frac{105}{100}\Big)\frac{\text{v}}{\text{time}}$ increase in power in 2nd case $=\frac{1}{2}\text{m}\Big(\frac{5}{100}\Big)\text{v}\Big(\frac{5}{100}\Big)\text{v}$ change in $\%$ of power $=\frac{\text{increase}}{\text{initial power}}100\%$
$=0.25\%$ I have considered the change of $5\%$ as increase.

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