Question 3
Figure shows a child blowing air with a straw near the opening of another straw which has its other end in a soft drink bottle. It was observed that the level of the soft drink in the straw rises up as soon as air is blown over its open end. Which one of the following best explains the reason for rise in level of the drink?
(a) Blowing of air decreases pressure over the opening of the straw.
(b) The straw of the soft drink bottle collapses when air is blown over its open end
(c) Blowing of air warms up the air inside the straw.
(d) Blowing of air increases the pressure on the surface of soft drink in the bottle.
It's because blowing of the air will decrease the pressure at the opening of the straw. Due to this decrease in pressure the gas from the bottle will rise up to fill the low-pressure area. In this process, the level of the drink rises in the bottle due to upward movement of air in the bottle.