Topic: Theory of Machines and Vibrations
The block has a kinetic energy of 3J and the spring connecting the block has an elastic energy of 2J (shown in figure). When the block is at $x=+2.0$ cm. What is the kinetic energy when the block is at $x=0$.
- A. 3J
- B. 2J
- C. 1J
- D. 5J
Answer: D. 5J
Explanation: From energy conservation: Total energy at ($x=2~cm$) = Total energy at ($x=0$). At $x=2~cm$, total energy $E = KE + PE = 3J + 2J = 5J$. At $x=0$, the potential energy of the spring is zero, so all the energy is converted into kinetic energy. Therefore, the kinetic energy at $x=0$ is 5J.