Question

A curtain is hanging at the entrance of a room. A long corridor runs at right angles to the door, that is parallel to the curtain. If a strong wind blows along the corridor, the curtain will

• A. Get pushed inside the room
• B. Get pushed outside the room
• C. Get collected towards one end/swirled
• D. Remain unaffected

Answer 1

The correct option is B

Get pushed outside the room

1. According to the basic crux of Bernoulli's theorem, the higher the velocity, the lower the pressure, and vice versa.
2. $Pressure\propto \frac{1}{velocity}$
3. The interaction of the high-velocity air ($v_1$) coming from the corridor with the outer face of the curtain creates a low-pressure zone ($p_1$) near the outer face of the curtain as depicted by the diagram shown above.
4. $p_1\propto \frac{1}{v_1}\Rightarrow$high-velocity air will create a low-pressure zone.
5. The interaction of the low-velocity air ($v_2$) coming from the room with the inner face of the curtain creates a high-pressure zone ($p_2$) near the inner face of the curtain as depicted by the above diagram.
6. $p_2\propto \frac{1}{v_2}\Rightarrow$low-velocity air will create a high-pressure zone.
7. The pressure on the inner face of the curtain ($p_1$) is greater than the pressure on the outer face of the curtain ($p_2$) and consequently, the curtain will get pushed outside the room.

Hence, option B is correct.