Question

a volunteer firefighter holds the end of a firehose as a strong jet of water emerges. when another firefighter steps on the hose, forming a constriction (a place where the area of the hose is smaller), the ejected water is faster. explain.

multiple choice

the force from the firefighter’s foot decreases the water pressure in the hose, leading to a faster exit velocity.

the constriction adds up to the atmospheric pressure which causes faster flow.

the constriction reduces friction between the water and the hose, allowing for faster flow.

if a constriction develops in the hose, the water speed in the constriction will be increased due to the smaller area.

Explanation:

This follows the principle of continuity in fluid dynamics ($A_1v_1 = A_2v_2$), where a smaller cross - sectional area ($A$) leads to a higher velocity ($v$) when the flow rate (product of area and velocity) is constant. The other options are incorrect: pressure change isn't the main reason, constriction doesn't add to atmospheric pressure, and friction isn't reduced by constriction.

Answer:

D. If a constriction develops in the hose, the water speed in the constriction will be increased due to the smaller area.