Knowledge Point 01: Reasons for the Erratic Movement Path of a Balloon During Rebound
The erratic movement path of a balloon during rebound is mainly due to uneven thickness causing uneven contraction and swing, as well as changes in balloon shape leading to variations in surface airflow speed, resulting in pressure differences that cause the balloon to swing.
Detailed Explanation: When a balloon is inflated and then released, the internal airflow escapes, causing the balloon to move due to rebound. During the inflation process, the balloon’s thickness is uneven in various places, leading to uneven contraction during deflation and thus producing swings.
Additionally, as the balloon changes shape during movement, the airflow speed on its surface also varies. According to fluid mechanics principles, the pressure is lower where the flow velocity is greater.
Therefore, the air pressure acting on the balloon’s surface constantly changes, further causing the balloon to swing and resulting in an erratic movement path.
Knowledge Point 02: Principle and Solution for a Thermos Bottle Cap Jumping Off
The thermos bottle cap jumps off because cold air enters the thermos and undergoes heat transfer with hot water, causing the gas to expand and exert force to eject the cap. Gently placing and shaking the cap can displace the cold air.
Detailed Explanation: After pouring out a large cup of hot water from a thermos, the temperature inside decreases, allowing outside cold air to enter. This cold air undergoes heat transfer with the hot water, increasing in temperature and causing the gas to expand.
When the gas pressure increases to a certain level, it exerts force externally, ejecting the cap from the bottle.
To avoid this, gently place the cap and shake the thermos a few times to cause the hot water to evaporate and produce steam, forcing the cold air out of the thermos. In this way, tightly securing the cap afterward will prevent it from jumping off.
Knowledge Point 03: Principle of Double-Glazed Windows for Heat and Sound Insulation
The principle of double-glazed windows for heat and sound insulation lies in the fact that the air layer between them does not easily conduct heat, effectively isolating heat transfer, while also serving as a sound barrier.
Detailed Explanation: Heat- and sound-insulating glass typically adopts a double-glazed structure with an air layer in between. Due to air’s low thermal conductivity, the air layer between double-glazed windows does not easily conduct heat, effectively isolating heat transfer and serving insulation purposes.
Additionally, the air layer acts as a sound barrier because sound requires a medium to propagate, and the presence of the air layer obstructs sound propagation, reducing sound transmission efficiency. Therefore, double-glazed windows are widely used in situations requiring heat and sound insulation.
