Q103 / 150 · MHT CET 2021 (21 Sep Shift 1) · Physics
A sphere of mass 25 gram is placed on a vertical spring. Spring is compressed by $0.2 \mathrm{~m}$ using a force $5 \mathrm{~N}$. When the spring is relaxed, mass is reaching a height of $\left(\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\right)$
- A$6 \mathrm{~cm}$
- B$8 \mathrm{~cm}$
- C$10 \mathrm{~cm}$
- Correct answerD$2 \mathrm{~m}$
Solution
Gravitational potential energy gained by the ball $=$ Elastic potential energy in the spring
$$
\begin{aligned}
& \mathrm{mgh}=\frac{1}{2} \mathrm{Fx} \\
& \therefore \mathrm{h}=\frac{\mathrm{Fx}}{2 \mathrm{mg}} \\
& =\frac{5 \times 0.2}{2 \times 25 \times 10^{-3} \times 10} \\
& =2 \mathrm{~m}
\end{aligned}
$$
Hence, the correct answer is option: 'D'.