A rubber balloon filled with hydrogen gas is left free in air. Then the balloon

Options

A. escapes into space.
B. ascends upto a certain height in air and floats.
C. ascends upto a certain height and then descends back to ground.
D. ascends upto acertain height and explodes

Answer

### Step-by-Step Solution:

1. **Understanding the Properties of Gases**:
- The balloon is filled with hydrogen gas, which has a lower density compared to the density of the surrounding air.

2. **Initial Behavior of the Balloon**:
- When the balloon is released, it will rise in the air because the buoyant force acting on it (due to the denser air) is greater than the weight of the balloon filled with hydrogen.

3. **Effect of Altitude on Air Density**:
- As the balloon rises, the density of the air decreases with altitude. This is a common phenomenon in the atmosphere where air becomes less dense at higher elevations.

4. **Equilibrium Point**:
- The balloon will continue to rise until it reaches a point where the density of the air equals the density of the hydrogen gas inside the balloon. At this point, the buoyant force will equal the weight of the balloon, and it will stop rising.

5. **Conclusion**:
- Therefore, the balloon will ascend to a certain height in the air and then float at that height, as the forces acting on it become balanced.

### Final Answer:
The correct answer is: **The balloon ascends to a certain height in air and floats.**

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