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Work, Power And Energy — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceWork, Power And Energy5 Marks
Question
Two objects having equal masses are moving with uniform velocities of $2m/s$ and $6m/s$ respectively. Calculate the ratio of their kinetic energies.
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Answer

Let masses of the two objects be m. $\text{v}_1 = 2\text{m}/\text{s}$ $\text{v}_2 = 6\text{m}/\text{s}$ $\text{KE}_1=\frac{1}{2}\text{m}\times\text{v}_1^2$ $=\frac{1}{2}\text{m}\times2^2$ $\text{KE}_2=\frac{1}{2}\text{m}\times\text{v}_2^2$ $=\frac{1}{2}\text{m}\times6^2$ $\text{Ratio}=\frac{\text{KE}_1}{\text{KE}_2}$ $=\frac{2^2}{6^2}=\frac{4}{36}=\frac{1}{9}$

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