Final answer:
A stream of water broadens as it rises in a decorative fountain due to the effects of gravity and air resistance. Conversely, a stream of water falling straight down from a faucet narrows because there is no air resistance acting on it.
Step-by-step explanation:
When water is shot nearly vertically upward in a decorative fountain, the stream broadens as it rises due to the effects of gravity and air resistance. As the water rises, gravity acts on it, causing it to spread out. Additionally, air exerts drag on the water as it rises, which also contributes to the broadening effect. Conversely, a stream of water falling straight down from a faucet narrows because there is no air resistance acting on it, allowing it to fall in a more concentrated stream. In this case, surface tension in the falling stream is not the main factor affecting the narrowing effect.