On the pan of a spring balance , is placed a beaker containing water . How will the reading of spring balance change if we dip our finger in this water ?

Options

A. increase
B. decrease
C. remain constant
D. depend upon the material o beaker

Answer

To solve the problem, we will analyze the situation step by step:

1. **Understanding the Initial Setup**:
- We have a spring balance with a beaker filled with water on it. The spring balance measures the total weight of the beaker and the water inside it.

2. **Dipping the Finger into the Water**:
- When we dip our finger into the water, we are displacing some of the water. According to Archimedes' principle, the displaced water exerts an upward buoyant force on the finger.

3. **Buoyant Force**:
- The buoyant force (FB) acts upwards on the finger. This force is equal to the weight of the water displaced by the submerged part of the finger.

4. **Normal Force**:
- According to Newton's third law, for every action, there is an equal and opposite reaction. Therefore, the finger experiences a normal force (FN) from the water that is equal in magnitude and opposite in direction to the buoyant force.

5. **Effect on the Spring Balance**:
- The spring balance measures the total weight acting on it. Initially, it measures the weight of the beaker and the water. When the finger is dipped into the water, the buoyant force acting on the finger results in an increase in the normal force acting on the water, which in turn increases the total weight acting on the spring balance.

6. **Conclusion**:
- As a result, the reading of the spring balance will increase when the finger is dipped into the water.

### Final Answer:
The reading of the spring balance will increase when you dip your finger in the water.

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