Two helium filled balloons are floating next to each other at the ends of strings tied to a table. The facing surfaces of the balloons are separated by 1 to 2 cm. If you blow through the opening between the balloons, then

Options

A. They move away from each other
B. They move towards each other
C. They are unaffected
D. Nothing can be said about their separation

Explanation

To solve the problem of two helium-filled balloons floating next to each other and the effect of blowing air between them, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Setup**:
- We have two helium balloons floating next to each other, separated by a distance of 1 to 2 cm.
- The balloons are tied to a table with strings.

2. **Identify the Action**:
- We are blowing air through the opening between the two balloons.

3. **Apply Bernoulli's Principle**:
- According to Bernoulli's principle, an increase in the velocity of a fluid (in this case, the air we blow) results in a decrease in pressure.
- The principle can be expressed as:
\[ P + \frac{1}{2} \rho v^2 + \rho gh = \text{constant} \]
- Here, \( P \) is the pressure, \( \rho \) is the fluid density, \( v \) is the fluid velocity, and \( h \) is the height.

4. **Analyze the Effect of Blowing Air**:
- When we blow air between the balloons, the velocity of the air increases in that region.
- As per Bernoulli's principle, this increase in velocity leads to a decrease in pressure in the space between the balloons.

5. **Compare Pressures**:
- Initially, the pressure in the space between the balloons is equal to atmospheric pressure.
- After blowing air, the pressure between the balloons (let's call it \( P \)) becomes less than the atmospheric pressure (\( P_{atm} \)).
- Therefore, we have:
\[ P < P_{atm} \]

6. **Determine the Movement of the Balloons**:
- The pressure outside the balloons remains at atmospheric pressure, which is greater than the pressure between them.
- This pressure difference creates a net force that pulls the balloons towards each other.

7. **Conclusion**:
- As a result, when air is blown between the balloons, they will move towards each other.

### Final Answer:
The correct option is that the balloons move towards each other.

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