Final answer:
Tapping a toothbrush on the sink helps it dry by applying force to overcome the surface tension holding water to the bristles. Surface tension and kinetic energy play a crucial role in the drying process and effectiveness of cleaning in general.
Step-by-step explanation:
Tapping your toothbrush on the sink helps dry it off by using a combination of actions: force and surface tension. When you shake or tap your toothbrush, you're applying a force to the droplets of water that are clinging to the bristles via surface tension.
This force exceeds the surface tension holding the water droplets together and adhering them to the brush, causing the water to overcome this tension and be expelled from the bristles, thus allowing the toothbrush to dry more quickly.
Surface tension is what holds the droplets to the bristles, but by adding kinetic energy to the system through tapping, we are breaking the tension and flinging the droplets away.
Similarly, while cleaning dishes, water alone is not effective in cleaning an oily bowl because water does not break down oils effectively without the help of soap or detergent, which reduces the surface tension and allows water to mix with oil.