Correct Option
The correct option is (a).
Explanation
Mechanical energy is primarily classified into two forms: Kinetic Energy and Potential Energy. Kinetic Energy is the energy possessed by an object by virtue of its motion. Potential Energy is the energy stored in an object due to its position or change in configuration (shape).
Statement-wise Analysis
- 1. A bullet piercing a target: Correct.
A bullet piercing a target is in motion with a specific velocity. Since Kinetic Energy depends on mass and velocity ($KE = \frac{1}{2}mv^2$), any moving object possesses Kinetic Energy. This energy enables the bullet to penetrate the target by doing work against resistance. - 2. A stretched bow: Incorrect.
When a bow is stretched, work is done to deform it. This energy is stored in the bow as Elastic Potential Energy due to its change in configuration. It does not possess Kinetic Energy until the string is released and the arrow begins to move. - 3. A compressed spring: Incorrect.
Compressing a spring involves doing work against the spring's restoring force. This energy is stored within the spring as Elastic Potential Energy. A compressed spring at rest does not possess Kinetic Energy.
Key Takeaway
Kinetic Energy is strictly associated with motion ($v \neq 0$). Energy stored due to deformation (stretching or compressing) or position (height) is Potential Energy.