why is it difficult for a fire fighter to hold a hose that ejects large amounts of water at high speed?

The hose experiences a backward reaction force equal to the rate that water momentum leaves the nozzle. The walls of the hose must exert this force on the water to direct it out the nozzle, and the hose feels the reaction force. If the water came straight from the hydrant to the nozzle, then there would not have to be a large force, but this is almost never the case.

It is difficult for a firefighter to hold a hose that ejects large amounts of water at high speed due to several factors:

1. Water Force: The water flowing through the hose exerts a significant force, known as water pressure. This force can be intense, especially when the water is discharged at high speed. The powerful jet of water creates a strong reactive force in the opposite direction, making it challenging to control and handle the hose.

2. Weight and Size: Fire hoses are designed to be durable and able to withstand high pressure, which means they are often bulky and heavy. When water is flowing through the hose, it adds additional weight, making it harder for the firefighter to hold and maneuver it. The sheer size of the hose can also be physically demanding to handle, particularly when it's pressurized.

3. Nozzle Reaction: The nozzle at the end of the hose is responsible for controlling the direction and intensity of the water stream. When the nozzle is set to deliver a high-flow or high-velocity jet, it generates a strong reaction force in the opposite direction. This reaction force can push back on the firefighter, making it necessary to use proper body positioning and physical strength to maintain control.

To overcome these difficulties, firefighters undergo extensive training to develop the necessary strength, grip, and technique to handle fire hoses effectively. Additionally, equipment such as hose straps, friction gloves, and body bracing techniques are utilized to enhance grip and stability while operating the hose.