The spring balance does not read properly after its long use because

Options

A. elasticity of spring increases
B. elasticity of spring decreases
C. plastic power decreases
D. plastic power increases

Explanation

**Step-by-Step Solution:**

1. **Understanding Spring Balance**: A spring balance is a device used to measure weight or force. It operates based on Hooke's Law, which states that the force exerted by a spring is directly proportional to its extension or compression, provided the elastic limit is not exceeded.

2. **Effect of Long Use**: Over time, with continuous use, the spring in the balance undergoes repeated stretching and compressing. This can lead to changes in the physical properties of the spring.

3. **Change in Spring Constant**: The spring constant (k) is a measure of the stiffness of the spring. After prolonged use, the spring may lose some of its elasticity, resulting in a decrease in the spring constant. This means that the spring will not return to its original length as effectively as it did when it was new.

4. **Resulting Inaccuracies**: As the spring constant decreases, the spring balance will start to give inaccurate readings. This is because the force (weight) applied to the spring will not produce the same amount of extension as it did before, leading to a miscalculation of the weight being measured.

5. **Conclusion**: Therefore, the spring balance does not read properly after long use because the elasticity of the spring decreases, which alters the spring constant and affects the accuracy of the measurements.

---